Sustainable Development and the Nature of Environmental Legal Principles

In this article, "things" lawyers call "principles" of environmental law will be discussed from a theoretical perspective. Three fundamental questions are answered: 1. Where does the high moral value that is usually attributed principles come from? 2. What is the exact difference between a principle and a legal rule, and between a principle and a policy? 3. What is the relationship between a principle and more concrete legal rules and policies? It is argued that principles of environmental law receive their high moral value from the ideal of sustainable development. An ideal is a value that is explicit, implicit or latent in the law, or the public and moral culture of a society or group that usually cannot be fully realized, and that partly transcends contingent, historical formulations, and implementations in terms of rules and principles. Principles form a necessary link between directly applicable and enforceable environmental legal rules and the underlying ideal. They are a necessary medium for ideals to find their way into concrete rules and can be used to bridge the gap between the morality of duty and the morality of aspiration. Because of their basis in (written or unwritten) law and their possible direct and intense influence on legal rules concerning activities that may harm the environment, they must be placed within the morality of duty: a bridgehead within the morality of duty reaching out for the morality of aspiration. From the general function of principles of forming a beachhead in the morality of duty, nine more concrete functions can be derived. These functions principles, both of a substantive and of a procedural nature, have, make it possible to distinguish them from legal rules. It must be acknowledged, however, that there is no very strict separation between principles on one side and rules on the other: environmental norms can be placed on a sliding scale with rules on one side and principles on the other side. Principles can become rules over time, when directly applicable in concrete cases. The nine functions are following: 1. principles can enhance the normative power of statutory rules; 2. principles can help to fill in open or unclear statutory rules; 3. principles can increase legal certainty and enhance the legitimacy of decision-making; 4. principles form the basis for new statutory rules; 5. principles give guidance to self-regulation; 6. principles create flexibility in the law; 7. principles help to implement international obligations; 8. principles stimulate the integration of environmental considerations into other policy fields; 9. principles are necessary to pursue an ideal. Principles thus influence the meaning of a rule but, at the same time, the application of a rule in a concrete case gives the relevant principle a clearer meaning than the principle has on its own. This goes for rules in various legal documents, such as acts and regulations, as well as transnational regulations, and selfregulatory rules. Principles thus are dynamic beacons in a wild ocean of ever changing concrete environmental rules. Although the underlying ideal of sustainable development has a rather anthropocentric character, the danger of influencing environmental legal principles (and through principles legal rules and policies as well) in a highly anthropocentric way is small. Firstly, because man is an inseparable part of nature and is very much dependent on balanced and intact ecosystems, especially when future generations are considered as well. Secondly, there is a moral relationship between man and nature. Natural objects have an inherent value: not destroying these objects contributes to the virtue of man. The ecological aspects of the ideal of sustainable development can be sufficiently advanced in decision-making processes by governmental authorities and courts, because most principles that rule environmental decision-making processes create enough room to take into account the more eco-centred arguments.

principle and a policy? 3. What is the relationship between a principle and more concrete legal rules and policies? It is argued that principles of environmental law receive their high moral value from the ideal of sustainable development. An ideal is a value that is explicit, implicit or latent in the law, or the public and moral culture of a society or group that usually cannot be fully realized, and that partly transcends contingent, historical formulations, and implementations in terms of rules and principles.
Principles form a necessary link between directly applicable and enforceable environmental legal rules and the underlying ideal. They are a necessary medium for ideals to find their way into concrete rules and can be used to bridge the gap between the morality of duty and the morality of aspiration. Because of their basis in (written or unwritten) law and their possible direct and intense influence on legal rules concerning activities that may harm the environment, they must be placed within the morality of duty: a bridgehead within the morality of duty reaching out for the morality of aspiration.
From the general function of principles of forming a beachhead in the morality of duty, nine more concrete functions can be derived. These functions principles, both of a * Professor of European and International Environmental Law, Tilburg University, The Netherlands, and member of the Netherlands Advisory Council for Housing, Spatial Planning and the Environment, director of the Centre for Legislative Studies of the Schoordijk Institute for Jurisprudence and Comparative Law (Tilburg University) and a member of the Commission on Environmental Law of the IUCN as well as a member of the board of the Netherlands Committee of the IUCN. substantive and of a procedural nature, have, make it possible to distinguish them from legal rules. It must be acknowledged, however, that there is no very strict separation between principles on one side and rules on the other: environmental norms can be placed on a sliding scale with rules on one side and principles on the other side.
Principles can become rules over time, when directly applicable in concrete cases. The nine functions are following: 1. principles can enhance the normative power of statutory rules; 2. principles can help to fill in open or unclear statutory rules; 3. principles can increase legal certainty and enhance the legitimacy of decision-making; 4. principles form the basis for new statutory rules; 5. principles give guidance to self-regulation; 6. principles create flexibility in the law; 7. principles help to implement international obligations; 8. principles stimulate the integration of environmental considerations into other policy fields; 9. principles are necessary to pursue an ideal. Principles thus influence the meaning of a rule but, at the same time, the application of a rule in a concrete case gives the relevant principle a clearer meaning than the principle has on its own. This goes for rules in various legal documents, such as acts and regulations, as well as transnational regulations, and selfregulatory rules. Principles thus are dynamic beacons in a wild ocean of ever changing concrete environmental rules. Although the underlying ideal of sustainable development has a rather anthropocentric character, the danger of influencing environmental legal principles (and through principles legal rules and policies as well) in a highly anthropocentric way is small. Firstly, because man is an inseparable part of nature and is very much dependent on balanced and intact ecosystems, especially when future generations are considered as well. Secondly, there is a moral relationship between man and nature. Natural objects have an inherent value: not destroying these objects contributes to the virtue of man. The ecological aspects of the ideal of sustainable development can be sufficiently advanced in decision-making processes by governmental authorities and courts, because most principles that rule environmental decision-making processes create enough room to take into account the more eco-centred arguments.

Introduction
Since the 1992 Rio Conference on Environment and Development (UNCED), environmental legal principles, such as the precautionary principle, the polluter-pays principle or the principle of public participation, play an ever-increasing role in international and national environmental law and policy, as does the concept of sustainable development. Covenant on Environment and Development. 3 With all these rapid developments in international and national environmental law, it becomes increasingly necessary to more precisely determine what is the legal function of the concept of sustainable development, which I will later call an "ideal", and of the principles of environmental law.
What is the relationship between the ideal of sustainable development and the legal principles and more concrete environmental legal rules, and between the principles and their role in legal practice and, more in general, fails to appreciate the legal meaning of principles and the basic difference between principles and legal rules. 7  art. 130R) only in a small amount of cases. 9 The EC-legislator does not systematically refer to these principles in environmental directives or regulations. In national environmental law, things are not much different. Although the legislator, in many countries all over the world, is now in the process of explicit codification of environmental legal principles, a substantive discussion on the question what is the purpose of such a codification is very often refrained from. 10 The confusion is partly caused by the fact that many norms or policy statements are called 'principles'. The frequent and often irrational use of the word 'principle' has given it a rather unclear status. Highly abstract notions like sustainable development or biodiversity, but also human rights and procedural rules on environmental impact 7  In this article, I would like to get a grip on the "things" lawyers call 'principles' of environmental law. For a long time, a principle was considered to be a special kind of norm, characterized by a rather general meaning, differentiating it from the more concrete legal rules. Principles go beyond concrete rules or policy goals; instead, they say something about a group of rules or policies, they denote what a collection of rules has in common, or what the common goal is of a collection of rules (for instance a statute). Principles usually contain a high moral and/or legal value.
This, however, leaves at least three fundamental questions unanswered.
1. Where does this high moral value come from?
2. What is the exact difference between a principle and a legal rule, and between a principle and a policy?
3. What is the relationship between a principle and more concrete legal rules and policies?
The first question is the most difficult one. Fuller has convincingly shown that in law, a distinction must be made between the morality of duty and the morality of aspiration.

12
The morality of duty 'lays down basic rules without which an ordered society is impossible, or without which an ordered society directed toward certain specific goals 11  must fail of its mark.' 13 The 'principles' 14 of a morality of aspiration 'are loose, vague, and indeterminate, and present us rather with a general idea of the perfection we ought to aim at, than afford us any certain and infallible directions acquiring it.'. 15 In more modern terms, such values could be described as the ideals of society or of a more specific community. In the next paragraph, I will try to show that in these ideals the basis for legal principles can be found (paragraph 2).
In paragraphs 3 and 4, the second and third questions will be dealt with. Basically, I will start from Dworkin's 16 distinction between rules, principles, and policies and elaborate on this distinction a little further, taking examples from the field of environmental law.
In paragraph 5 of this article, I will have a closer look at the specific character of the field of environmental policy and law. Since the ideal of sustainable development is of a rather anthropocentric nature, the question arises whether this ideal can actually be fit to be the goal that should be reached through applying legal principles and rules. Such policy goals (the WCED report mentions many more) can be seen as an effort to make the rather abstract ideal of 'sustainable development' more concrete. The same is done by the formulation of legal principles by a working group of the WCED, included in the report of the WCED itself. I will elaborate on these in the next two sections.
Since the publication of the WCED report, the idea of sustainable development, as an ideal, has been firmly recognized in non-binding UN declarations, as well as in many does not lay down basic rules without which an ordered society is impossible, or without which an ordered society directed toward certain specific goals must fail of its mark (morality of duty), but instead, that it is a loose, vague, and indeterminate, general idea of the perfection we ought to aim at. We, as well as generations to come, will need to aspire to reach the goal of sustainable development, without anticipating reaching it. 46 Van der Burg's definition of an ideal, however, only partly fits the above description of the value of sustainable development. It is true that sustainable development is a value that cannot be fully realized and that partly transcends contingent, historical formulations and implementations in terms of rules and principles. On the other hand, however, the 'ideal' of sustainable development has been laid down in various important legal documents, not as rules or legal principles, but as an ideal. The latter position seems to be supported by the wording of the Rio Declaration (see above). Still, in the next section I will argue that 'sustainable development' is an ideal and not a principle.

The relationship between ideals and principles
In the previous section, I have shown that the idea of sustainable development is a vague and undeterminate goal society aims at to reach perfection; a goal of high moral standard that the entire world community has embraced. To promote this goal, that never can be fully reached, a call upon the morality of duty must be made. In other words: more concrete economic, legal, and social instruments must be brought into action to generate a more sustainable use of the resources of the Earth.
In this article I focus on the legal instruments. 47 I will show that a first step to make the ideal more concrete is the formulation of (legal) principles, and that, in order to apply these principles, certain (even more concrete) rules are developed.
Principles can be seen as the link between ideals and duties, between the morality of aspiration and the morality of duty, between values and rules. 48  rules and thus form the link between the morality of aspiration and the morality of duty.
Principles are a necessary medium for ideals to find their way into concrete rules. They can be used to bridge the gap between the morality of duty and the morality of aspiration. Because of their basis in (written or unwritten) law and their possible direct and intense influence on legal rules concerning activities that may harm the environment, they must be placed within the morality of duty: a bridgehead within the morality of duty reaching out for the morality of aspiration. 3. principles form the basis for self-regulation or otherwise help to determine how private parties should behave in the social order.
For now, I would like to take the position that principles are part of written, statutory law and that they can be invoked in court and thus form a part of the morality of duty, albeit 50 Contrary to Van der Burg, who argues that principles and policies, together with ideals, all are categories of the sphere of aspiration, leaving only legal rules in the sphere of duty. Van 3, 4, 5, 8, 9, 12, 20, 21, 22, 24 and 27). The WCED, too, has adopted a set of legal principles; they are included in the report 'Our Common Future'. 57 As mentioned above, it was this report that worked as a catalyst in making the ideal of sustainable   to very concrete and precise; they cover almost all the space between an ideal, on the one hand, and a rule, on the other. The first principle has a higher 'morality of aspiration' character than the second one.
While the first principle sets a vague and indeterminate goal, without giving the one perfect way of reaching it, the second one is much closer to day-to-day legal practice. It has much more the character of the morality of duty, and, one could argue, has almost reached the status of a legal rule, i.e. the rule saying that the contracting State must set up a system of environmental impact assessment. One could even argue that the latter is not a principle at all, but a concrete legal rule. In the field of environmental law alone, there are dozens of principles giving direction to legal decisions, such as the granting of a permit by a governmental authority, a court decision on a case between a polluter and 73 Scholten P Rechtsbeginselen (Tjeenk Willink Zwolle 2 nd ed. 1941) 270.
an environmental action group, the issuing of legislation by the national or lower legislator. Do all these "things" that are called principles have to have the same role in law?
It cannot be denied, that in negotiation processes on environmental treaties or declarations with many nations involved, principles, because of their vague character and because of the fact that they are not directly legally binding, can be agreed upon more easily. Mann correctly noted that sometimes principles have more meaning and impact as a record of the political bargains that underlie a Convention, than as hard or soft-law obligations in themselves. 75 When looking at "things" that are called principles, this must be kept in mind.
In the end, I think there are four arguments, to explain the difference in the character of principles: 1. principles can take various forms, varying from very abstract to very precise, and from a high morality of aspiration to a high morality of duty; 2. people who draft laws and treaties are not aware of the character of principles and make legal rules which they inaccurately call principles; 3. people who draft laws and treaties are aware of the character of principles, but because of the failure to conclude to legally binding rules, they call the rules 'principles', indicating the non-binding character of the rules; 4. a combination of the above.
In my opinion, the fourth possibility is the most likely one, considering national and international environmental legal practice today. that it is essential that each principle must be valued in its own respect. The more concrete a principle is, the more it can be treated as a rule and the easier it is to directly apply it in a concrete case.
Without going too deeply into the matter of the degree to which principles are legally binding (the rest of the essay deals with that question), it has to be noted that, although there are as many differences as there are principles, Dworkin's theoretical distinction between principles and rules remains in tact. Generally it can be said that principles 'state a reason that argues in one direction, but does not necessitate a particular decision'; 76 the direction they point at is a desirable direction because of 'justice, or fairness or some other dimension of morality'. 77 The latter is of great importance to me: although principles form a part of the morality of duty, the substantive meaning of a principle lies closer to the morality of aspiration than is the case with concrete rules. This explains why principles form a beachhead within the morality of duty, reaching out towards the morality of aspiration. It also explains why a principle in a concrete case can yield to another principle, while retaining its significance.

78
I agree with the critics of Dworkin's distinction, that rules do not always have an all or nothing character, and that often rules cannot easily be applied in a concrete case either, and that rules, just as principles, may conflict without harming the value of either of these rules. 79 The basic difference between rules and principles lies in the higher moral character of principles and in their role as a link between ideals and legal rules.
This difference in character has many implications for the meaning of principles in legal 75 Mann Comment on the Paper by Philippe Sands 70. 76  practice. One of the implications is that principles can only function and only have a meaning in connection with rules. The meaning of a legal principle even depends on the context of the rules, applicable in a given case.
When we take a closer look at the environmental legal principles that usually are to be found in international and national legal documents, a rough distinction can be made between principles of a more substantive nature and procedural principles.   (Clarendon Oxford 1998(1996) 89-108.

How do principles originate?
I have stated that the high moral value of principles comes from an underlying ideal, using the example of sustainable development. But many of the now generally accepted principles of environmental law already existed before the ideal of sustainable development really became important internationally. Sands distinguishes between existing legal principles and new principles emerging in the context of sustainable development. 85 An existing principle is, for instance, the principle of co-operation (essentially Principles 9 and 27 of the Rio Declaration, but also present in Principles 5, 7, 12, 13, 14 and 24), that was included in many other international environmental documents as well. The principle can be traced back as early as 1933 to the Convention Relative to the Preservation of Flora and Fauna in their Natural States. 86 A relatively new principle is the precautionary principle, that, at the international level, began to appear in the mid-1980s. 87 This, however, does not mean that existing principles cannot have their roots in the ideal of sustainable development. Firstly, we have defined an ideal as a value that can be implicit in the law or the public and moral culture of a society. It is not farfetched to argue that the idea of sustainable development, however not explicitly formulated as such, 88 was already on the (international) scene since World War II. 89 88 The word 'sustainable' was used sometimes in international agreements on the conservation of whales and seals, such as the 1957 Convention on Conservation of North Pacific Fur Seals, 314 UNTS 105. These conventions mainly aimed at securing future exploitation of these animals by man. Art. II (1) states: 'In order to realize the objectives of this Convention, the Parties agree to coordinate necessary scientific research programs and to coordinate in investigating the fur seal resources of the North Pacific Ocean to determine: (a) what measures may be necessary to make possible the maximum sustainable productivity of the fur seal resources so that the fur seals populations can be brought to an maintained at the levels which will provide the greatest harvest year after year; and (b) (...)'. Sands gives another example: the 1946 International Whaling Convention, Sands International Law in the Field of Sustainable Development 59. be argued that, since the break through of the ideal of sustainable development, the existing principles were strongly influenced by this ideal. Their meaning has not been the same since. An example is the co-operation principle, which, as shown above, already existed for a long time in international environmental law. Since the UNCED, the idea of co-operation is not only aimed at the prevention of environmental damage in neighbouring states (bilateral or regional), but at a much broader aim: sustainable development for the world community (global In both cases there has to be some durable practice in the (legal) community to make a norm a principle and a sense of appropriateness; 94 even when a norm is first called a 'principle', that norm might have been considered principal for a longer period of time already. It is not possible to create a principle by formulating a norm as such in a statute or in a judgement, as it is not possible to decide to change a principle. At a given point we notice that, because of a change of law or normative perception, a principle has acquired a somewhat different meaning. I already mentioned the example of the principle of co-operation.

Conclusion: the ideal of sustainable development as the basis for legal principles of environmental law
I can now answer my first question. The high moral value of principles comes from underlying ideals. An ideal is a value that is explicit, implicit or latent in the law, or the public and moral culture of a society or group, that usually cannot be fully realized, and that partly transcends contingent, historical formulations, and implementations in terms of rules and principles. Since the explicit formulation of the ideal of sustainable

From principles to rules and policies
My second question was: what is the exact difference between a principle and a legal rule, and between a principle and a policy goal? I will deal with the first half of the question in section 3.1, and with the second half of the question in section 3.2. Again, I will use the principles related to the ideal of sustainable development as the prime source of examples to illustrate my line of reasoning. 96 Fuller The Morality of Law 9.

Principles versus rules
Dworkin has made a distinction between principles and rules. This distinction has been critized by many, but, as stated above, can in general be upheld (cf. section C).
Principles differ from rules in the sense that rules can be more easily directly applied in individual cases, while principles give a general direction for a decision, with a much lesser required outcome, than would be the case with legal rules. It must be acknowledged that this difference is not a very strict one. There is a sliding scale with a theoretical abstract and undeterminate principle on one side and a very concrete, highly practical rule on the other. Both principles and rules can range from abstract to more concrete. Principles can become rules over time, when directly applicable in concrete cases. As already mentioned, the basic difference between rules and principles lies in the higher moral character of principles and in their role as a link between ideals and legal rules.
The higher moral character of principles forms the basis for their functions in legal practice. I distinguish nine functions, that are roughly sketched below.  Act 1993). And the law that states, that in a specially protected area of natural beauty certain activities can only be carried out after a permit has been obtained, but that does not give any clue as to what criteria such a request must be tested against and under what conditions such a permit can be granted, acquires a greater normative power if principles are included in the statute itself, or if the rules in practice are influenced by unwritten principles.

Principles can help to define open or unclear statutory rules. This function
follows from the first one and is aimed at administrative authorities and courts.
Principles can be used by administrative authorities as well as the courts in the process of interpreting statutory rules in concrete cases, especially in cases where the rules are unclear or leave the competent authorities a great deal of room for discretion, or where there are conflicting rules.

Principles can increase legal certainty and enhance the legitimacy of decision-
making. Because of the normative guidance offered by legal principles, both the administration and the judiciary are more or less obliged to motivate a decision in the light of the relevant principles, offering citizens more certainty as to what are important arguments for the decision and thus enhancing its legitimacy.

Principles form the basis for new statutory rules.
Principles also give guidance to rulemakers, at national, European and international levels. They set the goals that have to be reached with (new) rules and thus create stability and legal certainty and they make sure that there is, to a certain extent, systematization of legal rules. They make it possible for rulemakers to make less detailed rules and thus create more flexibility in the law. Principles offer the necessary beacons for such a legislation.

7.
Principles have to play an important role in national legal systems and in the EU, because they help to implement international obligations. In many important international legal documents, although not always legally binding, principles have been laid down as important guiding norms. To do justice to these principles, they must be seriously considered by nations that have signed international legal documents such as the Rio Declaration. 9. Principles are necessary to pursue an ideal. Last but not least and already stated above, principles are a necessary link between ideals and concrete legal rules.

Principles stimulate integration of environmental considerations into other
What is clear from these functions is the close relationship between principles and rules. Sands even states that 'the substantive legal meaning of principles emerges only in their application to a given set of facts', 100 and I think he is right. Rules and principles almost become one in the process of application of both of them. A rule is applied in the light of a relevant principle, and thus the principle influences the meaning of the rule.

101
At the same time, the application of this rule (in the light of the relevant principle), gives the principle a clearer meaning than the principle has on its own: we see the relevance of a principle for legal practice especially when applying and interpreting rules in concrete cases or when making (new) rules. Therefore, using principles by no means implies that we are not using rules.102 On the contrary, Sands states that, in the end, the influence of a principle on rules might even have become so strong, that it becomes a rule with a clear and unconditional responsibility not to cause damage to the environment of other states (Principle 2 of the Rio Declaration and Principle 21 of the Stockholm Declaration), however, is not convincing. The fact that this principle is the 'cornerstone of international environmental law' and that it can be enforced before international courts and tribunals, 104 does not mean that it has become a rule. The basic moral character of the principle remains intact, and the principle of sovereignty clearly has all the nine functions mentioned above. Although a legal principle can become very clear and unconditional in legal practice, it will still be considered as a principle and not as a rule. A principle, by its nature, keeps its specific functions, and therefore it is important to keep the basic difference between principles and rules in mind.
This goes for rules in various legal documents, such as acts and regulations, as well as transnational regulations, and selfregulatory rules. Principles thus are dynamic beacons in a wild ocean of ever changing concrete environmental rules. De Sadeleer stresses this special position of 'directing principles': they can be an interface between modern and post-modern law, i.e., between fixed standards and pragmatic and reversible rules.

Principles versus policies
A third category distinguished by Dworkin, besides principles and rules, are policies. A policy, according to Dworkin, is 'that kind of standard that sets out a goal to be reached, generally an improvement in some economic, political or social feature of the community', while a principle 'is a standard to be observed, not because it will advance or secure an economic, political or social situation deemed desirable, but because it is a The difference between a policy and a principle might seem more problematic in practice, especially in a specific policy field like in that of the protection of the environment. Still, there are some big theoretical differences, which make it essential to differentiate between them. Principles are legal norms that, although not directly applicable (only via rules), have much more and a much more constant weight in legal practice. Principles have to be applied and cannot very easily be ignored because of their high moral content. When a relevant principle is passed over without good reason, a court will quash the decision. Policies have much less legal influence: a court will test a decision primarily against its accordance to binding legal principles and rules. Only in the two situations mentioned above (a statute explicitly obliged to take a certain policy document into account, or indirectly via the general principles of proper administrative action) policy documents can play a role in a judicial procedure against a government decision. In this case, however, it will be much easier for the government to give reasons acceptable to a court, not to follow the policy goal in a specific case. Also, policies may be changed overnight; principles, however, are embedded in the legal culture and, although their precise content may vary from time to time, principles remain relevant for a long period of time.
Principles even have a strong influence on policies. It is not very well conceivable that a policy is announced that is contrary to certain principles of environmental policy and law. Principles thus influence not only the making and application of concrete rules, they also affect policies. When a State has adopted the 'polluter pays' principle as a leading principle of environmental law, it will prove to be difficult for the competent authority to formulate a policy stating that, for the next five years, extra environmental taxes will be imposed on all people in order to raise funds to combat the consequences of acidification by the bio-industry. Such a policy will meet criticism in the political and social debate, but it will also be more difficult to implement in legal practice, since a decision implementing such policy would be contrary to the legal principle and might be quashed by the court.

From ideals to rules and policies
Policies do play an important part in the promotion of an ideal, such as the ideal of sustainable development, as do principles and rules. All are different standards necessary in our efforts to reach the ideal. Because of the different functions and the different legal meanings of these standards, I think it is crucial that in legal documents these differences are observed. It ís possible to formulate the ideal of sustainable development as a policy or a principle or as a rule, but this is not very practical. To focus on the ideal of sustainable development again, the entire structure of principles, rules and policies is as follows. To make the ideal of sustainable development more concrete and to have it implemented in concrete legal decisions, principles, such as the precautionary principle or the 'polluter pays' principle, form a necessary link between the ideal, on one hand, and rules and policies, on the other.
Both the formulation and the application of concrete legal rules are influenced by these principles. As far as abstract policies are concerned, ideals can more or less directly influence these (for instance, the policy of the minister of foreign aid to pay more attention to environmental issues when deciding on new aid programmes may be a consequence of the ideal of sustainable development). For the more concrete policies, this ideal is too abstract. In those cases, policies, like rules, are influenced by principles, but they also need enforceable legal rules in order to be achieved.

From man to nature
The ideal of sustainable development seems very anthropocentric: economic development of all nations, especially developing countries, must be stimulated, but the environment and natural resources may not be used in an unsustainable manner in order to preserve their potential use for future generations. With sustainable development, the ethical principles involved are about responsibilities among groups of human beings: developed versus developing and present versus future. 108 Still, with sustainable development being an ideal of international environmental policy and law, which influences principles and environmental legal rules, the question arises of whether or not this is acceptable. Is the ideal really an anthropocentric ideal? If this is the case, it might be unacceptable that the legal principles and rules in the field of environmental law are being influenced by an anthropocentric ideal.

Sustainable development: an anthropocentric ideal?
It has generally been exepted that human interests cannot be separated from the protection of the environment. Protection of the environment because of human interests therefore has spill-over effects to non-humans (animals and nature). 109 Even the 1946 International Convention for the Regulation of Whaling, which declares its purposes for the benefit of sustainable human exploitation, 110 thus has a spill-over effect. But it must be acknowledged that this is not a very satisfactory approach to the issue of the aim of environmental policy and law in general and the aim of the ideal of sustainable development in particular.
Nature and the environment are entities worth moral consideration in their own right, not just because we need them for our survival or for our well-being. 111 From this perspective one might ignore any reference to human interests or stewardship. This idea has been elaborated by some in the sense that, as natural objects have their own dignity, they should also be considered legal subjects, and have standing before the courts. Not just animals should be considered as legal entities possessing rights, 112

Is an anthropocentric ideal acceptable?
Although there has been a great deal of criticism on this anthropocentric tone in the If we extend the precautionary approach to future generations as well, the line of reasoning becomes even stronger. The extinction of species of plants or animals can limit the options of future generations, so sustainable development requires the conservation of plant and animal species, even if they are not of direct value to the life of present day man. 123 To preserve these options for future generations, legal measures protecting the environment must be made by the present generation. 124 The second argument can be that there is a moral relationship between man and nature. It has been argued that protecting nature is morally the best thing to do: it is an 'ideal of human excellence'. 125 This argument leads us back to the concept of ideals as elaborated above, ideals as values that are explicit, implicit or latent in the law, or the public and moral culture of a society or group that usually cannot be fully realized, and that partly transcend contingent, historical formulations, and implementations in terms of rules and principles. 'It is not farfetched to suggest that there is a human ideal which the beetle crusher does not attain. Nor is it idle to suggest that a person who has been exposed to B and reacted to B the grandeur of great valleys or the majesty of mountains is better for it, than if he had passed the time playing pushpin.' 126  This moral relationship is reflected in the 'last person on Earth scenario': the sole survivor on Earth of a nuclear war has the possibility, before dying, to push a button, destroying some surviving objects, like the Amazon rainforest, the last remaining herd of elephants or even non-natural objects with some intrinsic value like a painting by Van Gogh. It is morally wrong to do so because these objects have an intrinsic value and therefore not destroying them contributes to the virtue of man, to a flourishing human existence. 'The best human life is one that includes an awareness of and practical concern with the goods of entities in the non-human world. (...) care for the natural world for its own sake is a part of the best life for humans (...)'. 130 In both of the above interpretations, the seemingly anthropocentric ideal of sustainable development has a strong link to more ecocentric approaches of environmental law and policy. Environmental protection is necessary to achieve economic and moral goals of man, but in order to do so, all possible consequences for the environment must be considered carefully, thorouhgly and precautiously, keeping in mind the intrinsic value of nature. This approach, however, does not entirely solve the problem that we cannot determine objectively how clean precisely a river must be.
Stone has argued to solve the latter problem by introducing an ideal-oriented construct: '(...) while we cannot orient the law to a Thing's welfare, we can orient it to some ideal state of the Thing, without (...) undertaking to express that ideal in a specific set of numbers.' 131 This interesting approach, which, although on a different level, has some of the characteristics of the concept of ideal-oriented environmental law as described above, can also be used in a more ecological approach of the ideal of sustainable development.
In my view, to make sure that these ecological aspects of the ideal of sustainable development are sufficiently advanced in decision-making processes by governmental authorities and the courts, the principles that rule environmental decision-making processes must create enough room to take into account the more eco-centred arguments that can be found in all decision-making processes where environmental issues are at stake. Most of the environmental legal principles prevailing in international and national environmental law reflect this idea. The precautionary principle has already been mentioned as an example. Legal rules that are influenced by the precautionary principle must compel the government to constantly review its policy in the light of the interests of future generations and the environment (and to make laws that guarantee such a review), and to assess the impact administrative decisions may have on the 131 Stone ChD "The Nonperson in Law" in: Stone ChD (ed), Should Trees Have Standing? and other quality of the environment, including the intrinsic value of natural objects. Legislators may even explicitly state that when exercising certain powers, the competent authorities must act according to the principle that 'the intrinsic value of animals is recognized'.

132
Another example is the 'polluter pays' principle, which is not only relevant to damage to a person or a person's possessions, but also to damage to natural objects with no direct economic relevance, like Alaska's Prince William Sound, where in 1989 oil from the Exxon Valdez spoiled a great deal of the then present natural objects.
Procedural principles like the principles of participation in decision-making processes and access to justice in environmental matters for interested parties also The preambular paragraphs of this Convention recognize 'that every person has the right to live in an environment adequate to his or her health and well-being, and the duty, both individually and in association with others, to protect and improve the environment for the benefit of present and future generations,' and consider 'that, to be able to assert this right and observe this duty, citizens must have access to information, be entitled to participate in decision-making and have access to justice in environmental matters, and acknowledging in this regard that citizens may need assistance in order to exercise their rights (...) '. 134 This has explicitly and unmistakably been recognized in international environmental law with the adoption of the Convention on Access to Information, Public Participation in Decision-Making and Access to Justice in Environmental Matters in 1998, of which the first article reads as follows: 'In order to contribute to the protection of the right of every person of present and future generations to live in an environment adequate to his or her health and well-being, each Party shall guarantee the rights of access to information, public participation in decision-making, and access to justice in environmental matters in constitutional democracy: everyone has a responsibility towards (voiceless) future generations and natural objects, and everyone must at least be able to fulfil this responsibility, in order to promote the ideal of 'human excellence'.

Conclusion
Principles of environmental law receive their high moral value from underlying ideals, most notably the ideal of sustainable development. An ideal is a value that is explicit, implicit or latent in the law, or the public and moral culture of a society or group that usually cannot be fully realized, and that partly transcends contingent, historical formulations, and implementations in terms of rules and principles. The ideal of sustainable development has been explicitly laid down in many international, European and national legal documents, both of a binding and a non-binding nature. The ideal strongly influences existing and new principles of environmental law, and, through the principles, also more concrete legal rules and policies.
Principles form a necessary link between directly applicable and enforceable environmental legal rules and the underlying ideal. They are a necessary medium for ideals to find their way into concrete statutory and treaty rules and standards and can be used to bridge the gap between the morality of duty and the morality of aspiration.
Because of their basis in (written or unwritten) law and their possible direct and intense influence on legal rules concerning activities that may harm the environment, they must be placed within the morality of duty: a bridgehead within the morality of duty reaching out for the morality of aspiration. From the general function of principles of forming a beachhead in the morality of duty, nine more concrete functions can be derived. These accordance with the provisions of this Convention. ' (1999 ILM 517). centric character, the danger of influencing environmental legal principles (and through principles legal rules and policies as well) in a highly anthropocentric way is small. Firstly, because man is an inseparable part of nature and is very much dependent on balanced and intact ecosystems, especially when future generations are considered as well. Secondly, there is a moral relationship between man and nature. Natural objects have an inherent value: not destroying these objects contributes to the virtue of man.
The ecological aspects of the ideal of sustainable development can be sufficiently advanced in decision-making processes by governmental authorities and courts, because most principles that rule environmental decision-making processes create enough room to take into account the more eco-centred arguments.