We were asked whether IEL is up to the challenge of common environmental concerns: whether its norms are "precise enough to influence states' and other actors' behavior," and whether it is "forceful enough to impose itself in the face of important economic and political interests." These questions appear to assume that to succeed IEL must be "precise" and "forceful," and that it may not sufficiently meet either of these demands. In my remarks, I will reflect on these assumptions and consider both the conceptual structure of IEL and its processes for law-making, implementation, and enforcement.
IEL remains rooted in customary law concepts that aim to balance competing sovereign interests. Under the foundational harm principle, environmental concerns have legal relevance only to the extent that they coincide with a direct impact on a state's territory. Collective environmental concerns, such as climate change, are difficult to capture in this framework. Of course, the conceptual structure of IEL has expanded beyond the classical interstate paradigm. The emergence of a legal concept of common concern of humankind suggests that certain types of environmental decline are matters of community interest. Although the concept of common concern does not imply a specific rule for the conduct of states, it does signal that their freedom of action may be subject to limits even where other states' sovereign rights are not affected in the direct transboundary sense envisaged by the harm principle. Such limits flow precisely from the fact that the concept identifies certain types of environmental degradation as of concern to all, which would appear to imply that obligations are owed erga omnes. In turn, a closely related concept has emerged that may be said to structure what states owe to one another in the context of common concerns: their participation in problem-solving in accordance with their common-but-differentiated responsibilities (CBDRs) and respective capabilities.
However, the rub of the matter is that it remains uncertain whether or not any of the collective concern concepts that have emerged during the last fifteen years or so have crystallized into customary IEL. The unsettled legal status of these concepts is compounded by the uncertainties that continue to plague general international law when it comes to the legal impact of community interests, including through the concepts of jus cogens and norms erga omnes.
Turning to the processes of IEL, here too classical international law fits uneasily with global environmental protection. The fact that law making is strictly consent based, with customary law development necessitating wide agreement among states, accounts in large part for the only tentative development of common concern norms. It also helps explain why the existing customary norms, even the harm principle, are indeed open textured. Whether such norms lend themselves to enforcement is subject to question. But the more important limitation of the classical paradigm may be the fact that states rarely take the formal step of enforcing IEL by invoking the responsibility of another for breaches of international law. And, even if common concern norms existed at customary law, the range of enforcement options available to states to defend community interests remains opaque. Of course, it is debatable whether the law of state responsibility, or an enforcement-oriented approach, is suited to global environmental protection in the first place.
So far, I have painted a rather bleak picture, and one that seems to suggest that IEL is indeed neither "precise enough" to influence behavior, nor "forceful enough to impose itself." However, that conclusion would be wrong in a number of fundamental respects.
Returning to the conceptual structure of IEL, I would first of all take issue with the very notion that law must be "precise" to shape behavior. Obviously, in some circumstances precise technical standards are needed for very practical reasons, for example, to stabilize greenhouse gas concentrations in the atmosphere. …