Customary Law as Basis for International Environmental Law?

Let us start with a quick exploration of two doctrinal aspects before turning to the question whether customary law is well-suited to regulation of the kinds of problems we face in modern international environmental law. The first is “sources doctrine” (shorthand for sources of international law), which classical public international law conceived of as the answer how to find definitive statements of international law (and how international law is formed). The second is the concept of “sovereignty,” which can have any number of meanings in the legal context.

1/6 Regarding sovereignty, it is theoretically what renders public international law ultimately consensual. Theoretically, sovereign states are not subject to international law as restraint absent consent, with much theoretical effort then being dedicated to discerning consent. The immediate difficulty for environmental concerns is that, in the absence of binding rules, the tragedy of the commons is to be expected. There are formal tricks in terms of whether sovereignty is vested in individual states, versus being found perhaps in a “community of states.” But formalism aside, the chief issue is reaching agreement in articulating any binding legal rule, as with most of modern international environmental law.

2/6 The classic approach to sources doctrine in the classroom setting is to analyze Article 38(1) of the Statute of the International Court of Justice (ICJ) as its definitive statement, including as sources of international law:

a. Treaties, understood as international agreements among states (and some international organizations) intended to have the force of law (as opposed to political agreements as legally unenforceable undertakings)

b. Customary Law, understood as a general practice accepted as law, formed by consistent state behavior over time under legal compulsion as witnessed by opinio juris (a formal belief that the behavior is required by law, as opposed to perhaps being good politics or policy)

c. General Principles of Law “recognized by civilized nations” (here you recognize the ICJ League of Nations language, pre-post WW II decolonization)

d. Subject to limitations on precedent as such, judicial decisions and opinions of highly qualified academic sources as subsidiary means to determine legal rules

3/6 In practical application, judicial decisions and academic opinion are really just evidence of existing rules, since in public international law judges as a formal matter do not make law as in the common law system. When faced with a determination that a gap in the “law” exists on a given question, the proper technical response is “non liquet,” meaning the case is returned without a judgment because the judges are not authorized to fill the gap in the law as a technical matter. Formally speaking, public international law normally follows civil law principles, and academic sources normally just canvas state practice and agreements to discern rules. So judicial decisions and academic sources are more evidence of the law, rather than anything else, but that does not mean that any law review article or similar academic opinion suffices as authority.

4/6 Treaties are conceptually sound as voluntary undertakings once state parties reach agreement, and treaties are adaptable to rapidly changing circumstances, subject to the idea that states not parties to the agreement are not bound by it. There is also a hidden assumption that reaching agreement is even possible (which may be difficult in the case of states perceiving their essential interests as too divergent). So treaties would be a good way to articulate modern international environmental law in theory, but how to reach the necessary agreement (e.g., difficulties with the 1992 Greenhouse Gas Convention, 28 years-on as a framework convention, judging by US issues with the Kyoto Protocol and Paris Agreement)?

5/6 Customary law assumes state consent, subject to the idea that a state can withhold itself from coverage by consistent opposition to a customary law rule during its formation period. On a technical level, consistent state behavior means undertaking a meaningful action, rather than just voting for or against a resolution in the UN General Assembly. So, for example, the US Navy intentionally sailing ships through parts of the South China Sea is conduct challenging China’s claims to those waters as part of its territorial sea. But merely voting for a resolution or declaration at the UN opposing China’s claims would not constitute state behavior (although it may be evidence of opinion juris). Meanwhile, consistent state behavior does not lend itself well to the kinds of “parts per million” regulatory issues involved in much modern environmental law. But the chief problem in the modern setting is the requirement of consistent behavior over time, when state behavior may differ, and modern environmental problems may require answers in a period of time too short for the traditional formation of customary law.

6/6 The difficulty with general principles of law involves a disagreement about whether such a concept should be interpreted narrowly in terms of administrative-style rules like those you last thought about in civil procedure (such as res judicata), versus a broader concept almost like comparative law favoring recognition of “general principles” if enough states adopt a specific legal practice or rule (for example, in the environmental law area a requirement that environmental impact statements be required for any project needing government approval or permitting, because model environmental law statutes have spread to many countries). The formal advantage of general principles is that there is no formal provision for states withholding themselves from a rule’s coverage, but the narrower approach to general principles seems a better reflection of state expectations. There are more modern expressions of international law like human rights law post-World War II that may be congenial with the general principles approach, but we shall delay their consideration until Unit 3.

So now, let us look at readings containing the leading customary law precedents in the international environmental law area, then apply them to a few hypotheticals to see whether existing customary law, much less future customary law, might serve well as the basis for the prospective development of international environmental law.

Copyright 2020–21 © David Linnan.