The Precautionary Principle in Environmental Law

The precautionary Principle is, first and foremost, a scientific principle that deals with the risk of causing damage to the Environment. Before adopting this Principle in the 1990s, the traditional approach to preventing environmental damage was the prevention principle. The prevention principle presupposes prior knowledge of the risks involved in certain human activities at a level such that this knowledge makes it possible to anticipate the manifestation of environmental damage and to adopt the necessary measures to avoid or mitigate it. Since the precautionary Principle is based on the idea that environmental damage must be prevented even in cases where scientific knowledge does not allow a clear definition of the possible consequences of these activities on the Environment, some authors have been inclined to point out that the precautionary Principle is a more rigorous version of the prevention principle. However, unlike the prevention principle, which can be put into practice through the use of specific legal institutions, the degree of uncertainty that triggers the application of the precautionary Principle makes it very difficult to provide it with a legal framework for its enforcement. The precautionary Principle is not only grammatically complex to grasp but also vague as to the legal scope it may have. For this reason, we consider that almost thirty years after its adoption by the Rio de Janeiro Declaration, there is still much to be explained about this paradigm of environmental Law. This article aims to identify the legal scope of this scientific statement of such a complex wedge.

The literature suggests that the precautionary Principle1 was born in the mid-1970s. To illustrate this claim, it is often cited that in Germany, the precautionary Principle (‘Vorsorgeprinzip’) was incorporated into the German Federal Emission Protection Act of March 15 19742. Other authors consider that it was Principle 11 of the World Charter for Nature in 1982 that gave this Principle its current meaning. The cited document states (Table 1).

Table 1:Principle 11 of the world charter for nature.

Principle 11 of the World Charter for Nature clearly integrates several elements often attributed to the precautionary Principle, which the Rio de Janeiro Declaration later adopted.

According to Otiniano-Pozo [1], from the text of Principle XI of the Charter, three characteristics can be extracted that would configure the precautionary Principle as a principle of inaction or conservation:
A. First, it requires a prior analysis of the type of danger that would derive from the activity since not every danger legitimizes invoking the precautionary Principle, but only great dangers do.
B. Secondly, the promoter of hazardous activities is obliged to prove that its profits outweigh the potential damages, which constitutes a general reversal of the burden of proof and an important exception to the principle of freedom of enterprise.
C. Finally, the situation of scientific uncertainty about the risk represented by the phrase contained in the text of paragraph XI b), which mentions that “when their possible harmful effects are not fully known “, would imply the establishment of the prohibition to carry out such activities.

The OECD later adopted the precautionary Principle in a Ministerial Declaration at the Second International Conference on the Protection of the North Sea (London, 1987). Since then, this Principle has been frequently invoked in the context of marine pollution, climate change, toxic wastes, and hazardous activities [2].

This postulate was also incorporated in Principle 7 of the Ministerial Declaration on Sustainable Development adopted in Bergen on May 15, 1990, by the member states of the United Nations Economic Commission for Europe and the member of the European Commission (of the then European Communities) in charge of the Environment. Jiménez de Parga [3] points out that the precautionary Principle was also referred to in the Bamako Convention of January 30 1991, concluded within the African Union; the Framework Convention on Climate Change of 1992; and the Convention on Biological Diversity, also of 1992. However, its consecration culminated definitively in 1992 when the Rio de Janeiro Declaration recognized it.

The precautionary principle in the Rio de Janeiro declaration of 1992

The most popular version of the precautionary Principle is described in Principle 15 of the 1992 Rio de Janeiro Declaration, which states (Table 2). The precautionary approach contained in Principle 15 above is not understandable without looking at its antecedents, especially Principle 11 of the World Charter for Nature, whose wording is much more precise. In fact, the idea of reversal of the burden of proof, which most authors consider to be a proposal of this Principle, is not outlined in paragraph 15 of the Rio Declaration but is very clearly outlined in Principle 11 of the World Charter for Nature.

Table 2:Principle 15 of the 1992 Rio de Janeiro Declaration.

In an attempt to explain the precautionary Principle, Sands et al. [4] point out its central elements: the need for environmental protection, the presence of a threat or risk of serious harm, and the fact that lack of scientific certainty should not be used to avoid taking measures to prevent such harm. However, the description of its elements does not contribute much to the explanation of its legal nature. This has led some members of the international community, including the United States of America, to question its status as a “principle of international law” and a fortiori as a rule of customary international law (World Trade Organization, 2021). However, the Seabed Disputes Chamber of the International Tribunal for the Law of the Sea, in its 2011 advisory opinion, took note of a “tendency to consider this approach as part of customary international law”3, thus joining the growing group of those who recognize “precaution” either as an established principle of international Law or as a rule of customary international Law [5]. Even if it is a rule of customary international Law, the legal consequences of its adoption by the international community remain to be clarified. A review of international Law and jurisprudence reinforces this argument.

The precautionary principle in international treaties

The precautionary Principle is frequently introduced into international environmental framework conventions. Although this strategy is employed mainly in international environmental Law, it constitutes only a first step in the development of more precise rules at the international level embodying the precautionary Principle. Moreover, in several international agreements, the precautionary Principle is couched in terms that deprive it of immediate and autonomous applicability. Using expressions such as ‘shall form the basis of’, ‘shall inspire’, and ‘shall endeavour’ implies that the principle only intends to prepare States to comply with their international obligations. Only the repeated use of state practice and the corresponding doctrine can transform precaution into a rule of customary international law.

The precautionary principle in ICJ jurisprudence

The International Court of Justice has considered the precautionary Principle on several occasions. However, none of these cases have the Court’s decisions given the precautionary approach to the binding character enjoyed by a legal standard. For example, in the Case of the Cellulose Plants on the Uruguay River (judgment of April 20 2010 [6]), in which Argentina as the plaintiff sought that the burden of proof be reversed to Uruguay, the International Court of Justice stated that (Table 3).

Table 3:Case of the Cellulose Plants on the Uruguay River (judgment of April 20 2010).

Among other cases in which the precautionary Principle has been brought to the consideration of international tribunals, we can mention those of French nuclear tests (International Court of Justice, 1995); Gabčikovo-Nagymaros (International Court of Justice, 1997); meat hormones (World Trade Organization [7], Appellate Body, 1997); agricultural products (World Trade Organization [7], Appellate Body, 1998); southern tuna (International Tribunal for the Law of the Sea, 1999); MOX fuel plant case and Land Reclamation case (International Tribunal for the Law of the Sea, 2003)4. In none of these cases was the legal status of the precautionary Principle established.

For example, in the French nuclear waste case (New Zealand v. France), the International Court of Justice rejected the complaint filed in August 1995 by New Zealand on procedural grounds, so that it could not rule on the precautionary Principle, which was the basis of the complaint. In this lawsuit, the plaintiff sought that France refrain from all actions that could directly or indirectly involve radioactive contamination of the marine environment. For its part, France, in its defence, asserted that the precautionary Principle, according to the international Law in force at the time, was an uncertain principle from which no mandatory reversal of the burden of proof could be inferred.

Similarly, in the Gabcíkovo-Nagymaros case, Hungary invoked the emergence of new rules of international environmental Law, including the precautionary Principle, as justification for its unilateral suspension and subsequent withdrawal from the 1977 Treaty with the Czech Republic on the construction of the dam system. In its approach, the Hungarian government proposed combining the precautionary principle with the obligation not to cause damage to the environment of other countries. To this end, the State proposing to carry out a hazardous activity was obliged to demonstrate that it would not have harmful effects; otherwise, it would have to modify or abandon the project. For its part, Slovakia considered that Hungary had not proved that the precautionary Principle was part of International Law and had only demonstrated that it was a guiding principle.

In this case, the Court accepted and recognized the precautionary Principle but denied it the character of jus cogens5 and did not stop to examine its legal status. However, it recognized the importance of environmental monitoring and prevention and the difficulty of applying remedial mechanisms in this area due to the irreversible nature of the damage, as well as the need to assess ecological risks by current standards and on an ongoing basis. In other words, it only pronounced itself on the observance of the precautionary Principle, recognizing that, without having the character of ius cogens, it did have a binding character.

The precautionary principle in the jurisprudence of the Inter-American Court of Human Rights

The Inter-American Court of Human Rights (IACHR) has also not opted to give the precautionary approach the character of a legal norm. The IACHR has only analysed this Principle in “Advisory Opinion 23 on Environment and Human Rights”, issued on November 15, 2017, in response to the consultation made by Colombia on the obligations of the States of the continent concerning the Environment, and in the framework of the protection and guarantee of the rights to life and personal integrity [8]. In said document, the Court held “Therefore this Court understands that States must act according to the precautionary Principle to protect the right to life and personal integrity in cases where there are plausible indicators that an activity could cause serious and irreversible damage to the Environment even without scientific certainty.”

The precautionary principle versus the prevention principle

It is difficult to distinguish between the meaning of the precautionary Principle6 and that of prevention Principle since both involve anticipatory action in the face of a risk or danger of damage to the Environment7. However, the doctrine has highlighted profound differences between both principles.

For example, Jiménez de Parga [3] points out: “The precautionary Principle is based [...] on the lack of absolute scientific certainty of the ecological risk [...] since [...] if the risk is likely to occur, the precautionary Principle should not be applied but rather the principle of prevention.” According to this Principle, the precautionary approach refers to the measures to be adopted in cases where there is no scientific certainty about the impact an activity may have on the Environment [9]. On the other hand, when there is a certainty, the precautionary Principle is applied. According to Beatriz Arcila [10], the precautionary Principle is established so that appropriate preventive measures are taken to avoid such damage in situations of scientific uncertainty, where the Environment is threatened with serious or irreversible damage. In this sense, the jurist Jean-Marc Levielle, quoted by Leme [11], says that the precautionary Principle concerns the uncertainty of environmental damage since we are responsible for what we know or should know and what we should doubt. Thus, the precautionary Principle applies when there is uncertainty and, on the contrary, does not apply when there is a certainty.

On the other hand, the precautionary Principle, unlike the prevention principle, which refers mainly to individual actions, concerns environmental policy as a whole [13]. Its dimension goes beyond the problems associated with short-or medium-term risks since it also refers to long-term risks that may affect the well-being of future generations and does not refer to risks of any nature but to risks of serious or irreversible damage [3]. In the same vein, it has been said that the precautionary Principle is based on i) the vulnerability of the Environment, ii) the limitations of science to predict in advance and accurately the damage that the Environment may suffer, and iii) the possibility of alternatives of less harmful processes and products [14]. Accordingly, while the principle of prevention is based on the idea that in the face of the evaluation of known risks, it is possible to apply those legal instruments that allow minimizing the probability of occurrence of environmental damage [15]; the precautionary Principle does not require perfect knowledge of the risk, but the suspicion that it may exist is sufficient to take the necessary measures to avoid damage to the Environment [16].

In other words, according to the precautionary Principle, a presumption in favour of the Environment must be established in case of doubt or lack of scientific certainty. Therefore, preventive measures must be taken until it is demonstrated that the activities or products in question are harmless. This means that the burden of proof must be reversed, and whoever intends to carry out activities that, in accordance with the Law, put the Environment at risk must prove that such risk does not exist or is controllable [2]. On the other hand, while the prevention principle is based on risk assessment in the light of available scientific knowledge, the precautionary Principle recognizes science’s limitations in correctly assessing certain risks. It requires the implementation of actions despite the lack of scientific certainty. From this perspective, the application of the precautionary Principle implies a sort of balance between four factors: a) the risk, b) the probability that the damage will occur, c) the economic costs of the proposed measures, and d) the probability that the measures adopted will be effective in preventing the damage. The path to this end implies an adequate regulation of risk assessment techniques and, as a consequence, the legal recognition that the idea of precaution has a more significant impact on the legal system of liability for environmental damage, particularly in the presumption of the causal link and the reversal of the burden of proof. These issues go beyond the simple application of the strict liability system to suggest a liability model without damage or without proof of damage, which implies greater flexibility in the burden of proof than that recognized by the current legal systems.

The Second Chamber of the Supreme Court of Justice of the Nation (Mexico) has referred to this dilemma in the sentence pronounced on March 6, 2013, to resolve the Claim Resource (Recurso de Reclamación) 68/2012-Ca, derived from the Motion for Suspension of Constitutional Controversy file 109/2012 (Incidente de Suspensión de la Controversia Constitucional 109/2012). In this judgment, it can be read (Table 4). Consequently, applying the precautionary Principle is appropriate when the level of risk is assessable, and the legal system provides legal instruments that allow anticipating the occurrence of damage. Under such an assumption, the precautionary Principle is not applicable. On the contrary, when the probability of the occurrence of damage is not assessable due to the lack of scientific certainty, the precautionary Principle comes into play. However, which legal instruments should be applied in this case remains to be analysed. We will try to answer this question below.

Table 4:Motion for Suspension of Constitutional Controversy file 109/2012.

The content of the precautionary principle

A reading of Principle 15 of the Rio de Janeiro Declaration reveals many inaccuracies that complicate its proper interpretation. First, the precautionary Principle is preventive in nature, but unlike the former, protective measures to minimize or eliminate the risk of harm can be adopted even if there is no scientific certainty. However, it is open to further interpretation under what parameters we can define, which are the cases in which we are faced with a lack of scientific certainty that falls under the adjective of absolute and in which it is considered that this does not occur. In this sense, the precautionary criterion should be applied in cases where there is no scientific certainty about an activity’s impact on the Environment. (Inter-American Court of Human Rights, 2017 [7]) For example, Sofía Bordenave [17] maintains, “When the performance of an activity generates reasonable doubts about the possible existence of an environmental damage, the lack of scientific certainty may not be argued to justify the performance of the potentially dangerous act.”

Second, in Principle 15 of the Rio de Janeiro Declaration, the signatory states commit themselves to apply this criterion “broadly” but “in accordance with their capabilities.” The meaning of both expressions is also obscure. Finally, their application is to be defined in terms of costs, which is equally unclear. In short, the precautionary Principle is grammatically vague, and this prevents an acceptable interpretation of its legal implications. We will discuss this issue in the following section.

The legal nature of the precautionary principle

The precautionary Principle is a scientific principle that has had legal implications in most legal systems. However, most of the doctrine denies that Principle 15 of the Rio Declaration has the status of a legal norm; that is, they do not confer it a binding character. Boutillon [18], in an article published by the University of Michigan, points out, about the legal nature of the precautionary Principle, that the most recent jurisprudence indicates a move toward the recognition of the principle as a procedural standard. Similarly, Birnie et al. [19] note that “Despite its attractions, the wide variety of interpretations given to the precautionary principle and the novel and far-reaching effects of some applications suggest that it is not yet a principle of international law”. These contributions of environmental law doctrine are not always taken into account when attempting to put the precautionary Principle into practice.

Three decades after its incorporation into the Rio de Janeiro Declaration, it is still pending to clarify what are the legal consequences to which the recognition of the precautionary Principle leads. In this regard, Otiniano-Pozo [1] points out that: “Many international norms include the precautionary Principle in their content, either in their articles or in their preamble. Many of these norms are considered soft Law or non-binding, such as the Nairobi Declaration of 1982 or the Rio Declaration of 1992, which adopt precaution as an interpretative criterion.” Other authors take a contrary position and argue that the precautionary Principle has a binding character. Finally, one can also find in the literature those who argue that, although this Principle is not binding, it can influence the elaboration, interpretation and application of the international legislation of the member states of the organizations that conceived or endorsed it [20].

To resolve this dilemma, from the legal point of view, the question arises as to whether precaution will become a legally binding principle in customary international Law and the domestic Law of countries and not merely a guiding principle. In some legal instruments, the precautionary Principle appears to be on the way to becoming legally binding, for example, in the Cartagena Protocol on Biosafety8. From our perspective, the precautionary Principle can be considered as a material source of Law, but never as a formal source, much less as a legal norm in itself, because unlike what has happened with other principles recognized by the Rio de Janeiro declaration, such as the right to a healthy environment, the precautionary Principle has not been expressly incorporated into the Mexican constitutional text and the references that some laws make to it do not grant it that hierarchy. A principle is not a strict rule; it is a guide. It has the advantage of including theoretical explanations and foundations of Law, which help legislators make decisions. This means that a principle, when included in a legislative text or in an international treaty, can direct how the rules of that legislation or treaty are to be applied. In fact, some countries avoid using the term “precautionary principle” and refer to it as “precautionary approach” or “precautionary criterion”; ideas that carry less legal weight. However, it must be recognized that it is not possible to underestimate the influence that the general principles of Law exert in the formulation of legal institutions, either in the international context or in the domestic legislation and jurisprudence of the countries [20]. In this sense, one can cite the interpretation of this Principle made by the First Room of the Supreme Court of Justice in issuing its decision in Amparo under Revision 307/2016. In this decision, the Supreme Court of Justice held that (Table 5).

Table 5:Amparo under Revision 307/2016.

When the Supreme Court of the Nation states that the precautionary Principle may motivate administrative decisions, it recognizes that it does not constitute a legal rule. Indeed, two essential moments are present in any legal formulation: first, society’s recognition that a value deserves protection, and second, the construction of legislative instruments to protect this new value. The precautionary Principle necessarily corresponds to the first moment of legal formulation insofar as its objective is to protect the Environment even against unknown risks. In practice, any subsequent formulation, whether in international or domestic Law, begins by considering this Principle. Thus, although neither mandatory nor binding, the precautionary Principle is important in crystallizing new concepts and values. According to Article 38 of the Statute of the International Court of Justice, general principles of Law are also a source of international Law. Therefore, it seems indisputable that, among the principles deriving from international declarations, the precautionary Principle has a legal value that cannot be disregarded by countries in the international context and by legislators, policymakers, and courts in the domestic sphere. From the moment the precautionary Principle is recognized as an element of international Law, it also becomes part of the general principles of environmental Law, with unquestionable legitimacy in guiding the interpretation and application of all legal norms in force.

However, it is up to the legislator to decide how to translate the precautionary Principle into Law and how to implement it. The spectrum of possible strategies ranges from measures aimed at obtaining information to those prohibiting a particular activity or the use of certain hazardous substances. In this way, the precautionary Principle can lower the standard of proof and make it possible to shift the burden of proof. For the State to act, the conviction that a risk is actually real and present is not required. Instead, it is sufficient that there are plausible or serious indications of a risk to the Environment. If this exists, it is then up to the injurer to disprove the well-founded indications of concrete cause-andeffect relationships and to overturn the assumptions that have given rise to the concern. Consequently, the precautionary Principle is the basis for the development of new legal institutions aimed at defining how the State must deal with the lack of scientific certainty to protect the Environment.

The reception of the precautionary principle in Mexican law

Constitutional recognition: As mentioned above, the precautionary Principle has not been expressly incorporated into the text of the United Mexican States Political Constitution. Despite this, in an isolated thesis, the Third Collegiate Court of the Twenty- Seventh Circuit has held that this Principle finds constitutional support in Articles 1 and 4 of the Magna Carta. In the Judgment pronounced in the Amparo in review 261/2016, the aforementioned Court held (Table 6). However, this jurisprudential interpretation is not binding as it is only an isolated thesis. Moreover, as it is a fundamentally scientific principle, its constitutional consecration does not seem to be relevant. On the other hand, its interpretation is relevant to defining how to import this scientific Principle into the field of Law.

Table 6:Amparo in review 261/2016.

Environmental legislation: In the national secondary environmental legislation, only two ordinances allude to the precautionary criteria. In the first place, section III of Article 26 of the General Law on Climate Change mentions the precautionary Principle as one of the guiding principles of the national policy on this matter. However, it cannot be said that this Law gives the criterion a normative character. This precept defines the principle in the following terms (Table 7). Second, the Law on Biosafety of Genetically Modified Organisms states (Table 8). From the reading of this precept, it can be deduced that the precautionary Principle is not a legal rule but a criterion that can be fulfilled with the application of the different regulations that this legislation establishes throughout its chapters. On the other hand, it can also be argued that the precautionary Principle is a criterion for interpreting existing legislation or a source of new Law, but it is in no way a legal norm.

Table 7:Article 26 of the general law on climate change.

Table 8:Law on biosafety of genetically modified organisms.

The precautionary principle and the reversal of the burden of proof

Although the wording of Principle 15 of the Rio Declaration does not refer to it, among the legal consequences attributed to the precautionary Principle, one of the most interesting is the reversal of the burden of proof. Traditionally, the person who claims that an activity could cause damage to the Environment must present evidence to support that claim. In procedural Law, this is called the “burden of proof” and is summarized in the statement “he who asserts must prove”. Principle 15 of the Rio de Janeiro Declaration does not mention this attribute. Although in the judgment rendered in Amparo under Review 261/2016, the Third Collegiate Court of the Twenty-Seventh Circuit held that one of the elements of the precautionary Principle is the reversal of the evidentiary burden, in reality, this isolated jurisprudence thesis does not further develop that argument. The thesis states in pertinent part: “Therefore, the following are elements of this Principle: i) the intertemporal dimension; ii) the lack of absolute scientific certainty of the environmental risk; iii) the risks must be serious and irreversible; and iv) the reversal of the burden of proof to the infringer.”

Similarly, the First Chamber of the Supreme Court of Justice, in its judgment rendered on November 14, 2018, in Amparo under Review 307/2016, referred to the evidentiary burden in the following terms (Table 9). As can be seen, the Supreme Court’s interpretation refers to only one side of the coin. The harmonious interpretation of Principle 11 of the World Charter for Nature and Principle 15 of the Rio Declaration allows us to maintain that the precautionary Principle implicitly proposes the reversal of the burden of proof in a double sense. On the one hand, in the field of administrative Law, when there is no legal certainty, the person or entity seeking authorization to carry out an activity that involves a certain level of risk must demonstrate, within the corresponding procedure, that it is not harmful. This occurs very clearly in the Environmental Impact Assessment procedure regulated by the General Law of Ecological Balance and Environmental Protection. On the other hand, in the field of liability for environmental damage, the burden of proof must be borne by the party allegedly responsible for the damage caused, as has been recognized by some national legislations around the world.

Table 9:Amparo under Review 307/2016

Therefore, the idea of reversing the burden of proof must be analysed from at least two points of view: from the procedural and regulatory perspectives. In this sense, in the context of the imputation of liability arising from the generation of environmental damage, several countries have followed the trend of inverting the burden of proof in their legislation since the adoption of Principle 15 of the Rio Declaration. Mexico goes in the opposite direction since the Federal Law of Environmental Liability rejects this rule. Section 36 states: “The causal link between the damage caused and the conduct imputed to the defendant must be proved in the substantiation of the trial”. This means that, at least in this aspect, the precautionary approach has not yet been fully adopted by Mexican Law, even though it is found in a Declaration of Principles signed by Mexico and even though the Supreme Court of Justice’s jurisprudence holds that the precautionary Principle entails a reversal of the burden of proof. The second approach to reversing the burden of proof is regulatory. In the case of activities that involve a greater risk to the Environment, governments usually issue legislation in which the regulated party must prove that it will take the appropriate measures to mitigate or minimize that risk, thus reversing the burden of proof to the individual.

In the Mexican legal system, there are several provisions that fall under this assumption. For example, in the Environmental Impact Assessment, the promoter of a work or activity whose performance may cause ecological imbalance or exceed the limits and conditions established in the environmental regulations to protect the Environment must demonstrate to both the environmental authority and the host community that such work or activity will not generate irreparable environmental damage, given the mitigation measures that will restrict the development of such work or activity. This demonstration must include, in many cases, risk assessment. In this sense, the Second Chamber of the Supreme Court of Justice of the Nation ruled in Amparo under Review 921/2016 on April 5, 2017. In the respective judgment, the Second Chamber stated (Table 10). Similarly, in the case of pesticides, the Regulations on Registrations, Import and Export Authorizations and Export Certificates for Pesticides, Plant Nutrients and Toxic or Hazardous Substances and Materials impose a series of requirements on those interested in obtaining a sanitary registration to explain and explain the risk that these substances entail and how to mitigate it.

Table 10:Amparo under Review 921/2016

In addition to the above, the Mexican government is empowered by Article 131 of the Political Constitution of the United Mexican States and by the Foreign Trade Law to prohibit the entry into the country of goods that may be hazardous to the Environment, following a risk analysis. Finally, when processing an import permit for these goods, the authority must verify that they have a sanitary registration and that their importation has not been prohibited, thus complying with the precautionary criterion. Finally, the precautionary Principle is also behind the study and risk assessment referred to in the Law on Biosafety of Genetically Modified Organisms. However, from any of the perspectives analysed, the incorporation of the precautionary Principle into the legal system requires the development of legal provisions that give it form. As long as this does not occur, the precautionary Principle is limited to being a criterion for the interpretation of existing legislation but not a legal norm in itself. Therefore, the Supreme Court of Justice’s current interpretation of the relationship between the precautionary Principle and the reversal of the burden of proof is limited in scope.

Undoubtedly, the precautionary Principle enshrined in the 1992 Declaration of Rio de Janeiro has influenced the development of environmental Law in several countries worldwide. It is mentioned in several international treaties and local laws and is the object of concern of international, regional, and national courts. Likewise, this Principle has been the axis of diverse doctrinal analyses in the field of environmental Law. However, we cannot maintain that this paradigm has been fully understood thirty years after its consolidation. The precautionary Principle is a scientific principle, and its interpretation cannot be forced to attribute it to the character of a legal rule. However, it can influence the redesign of Mexican environmental Law to the extent that it is the philosophical source of suitable normative developments to address the problems related to the prevention of environmental damage. The precautionary Principle can guide these developments in two ways. In regulation, the burden of proving control of the risk involved can be transferred to those interested in carrying out activities that pose a risk to the environment. Several of the legislations analysed here reflect this trend. In the field of liability for environmental damage, reversing the burden of proof on the person who can cause such damage. Therefore, in the future of environmental Law, this change in interpretation of the precautionary Principle may contribute significantly to its consolidation as an autonomous legal discipline.

1. Otiniano-Pozo K (2016) Guidelines for effective regulation of the precautionary principle in Peruvian law based on the experience of European Community law, University of Piura, Peru, p. 26.
2. Kiss A, Sheldon D (1995) Treaty on European environmental law, Frison-Roche Editions, Paris.
3. Jiménez de Parga y Maseda P (2001) The principle of prevention in international environmental law, Ecoiuris, Madrid, Spain, pp. 78-79.
4. Sands P, Peel J (2012) Principles of international environmental law, (3^rd edn), Cambridge University Press, England, UK.
5. Günter Handl (2012) Declaration of the United Nations conference on the human environment (Stockholm Declaration), 1972, and Rio Declaration on environment and development, 1992. United Nations Audiovisual Library of International Law.
6. International Court of Justice (2010) Case of the pulp mills on the Uruguay River (Argentina Vs. Uruguay).
7. World Trade Organization, European Communities-Measures Affecting the Approval and Marketing of Biotech Products.
8. Inter-American Court of Human Rights (2017) Advisory opinion OC-23/17 environment and human rights.
9. Fernández Egea RM (2018) International environmental jurisprudence. Catalan Journal of Environmental Law, Volume 9.
10. Beatriz A (2009) The precautionary principle and its judicial application. Journal of the Faculty of Law and Political Science 39(111): 283-304.
11. Arie T (2002) Evolution and status of precautionary principle in international law. Kluwer Law International, The Hague, Netherlands.
12. Leme Machado PA (2006) Right to information and the environment, Malherios Editors, Sao Paulo, Brazil.
13. Paolo D (2002) The principles of environmental protection. In: Giampiero Di Plinio, Pasquale F (Eds.), Principles of Environmental Law, Giuffré Publisher, Italy.
14. Betancourt Rodríguez A (2001) Environmental law institutions, The Law, Madrid, Spain.
15. Roche C (2001) Environmental law, Gualino Publisher, Paris.
16. De Sadeleer N (1999) The polluter-pays, prevention, and precautionary principles. An essay on the genesis and legal scope of some principles of environmental law, Bruylant Publishers, Brussels, Belgium.
17. Bordenave Sofía, Colaboración de Romina (n.d.) Report on human rights and the environment in the Americas presented to the Inter-American Commission on Human Rights, p. 209.
18. Sonia B (2002) The precautionary principle: Development of an international standard. Michigan Journal of International Law 23(2).
19. Birnie PW, Boyle AE (1992) International law and the environment. Oxford University Press, USA, p. 98.
20. World Commission on the Ethics of Scientific Knowledge and Technology (2005) Report of the group of experts on the precautionary principle, UNESCO, Paris, p. 21.