Third State Obligations and the Enforcement of International Law

[Lea Brilmayer is the Howard M. Holtzmann Professor of International Law at Yale Law School. Isaias Yemane Tesfalidet (LL.M. ’10, J.S.D. Candidate, Yale Law School) is a fellow with the Forum for International Criminal and Humanitarian Law.]

International legal theorists have always had substantial interest in what can be called the “first party” question — whether States are themselves obliged to obey international law. But discussion of non-party responsibilities — what we analyze here as “third State” obligations — is very limited. There are a small number of exceptional situations (mostly involving human rights norms characterized as jus cogens or erga omnes) where non-parties are already recognized as having affirmative legal obligations to become involved; but there are no general legal duties that apply across the board. This state of affairs presents something of a puzzle: If we assume that the parties to a conflict are bound by the international legal norms that govern the dispute, then why aren’t third States? And how is international law to be enforced if other states undercut it by making their indecisions according to political expediency?

Our position is that international law does have something important to say about third State obligations. Non-parties, in our view, are under a legal obligation not to contribute to another State’s violation of international law. This obligation is satisfied if either the third State has no involvement at all in the dispute or it is involved on the side of the victim. This approach is quite different from the closest existing analog – what we call the “State bystander” model – which is limited to specific issue areas such as human rights and which rests on debatable premises concerning affirmative obligations. If third State obligations are accepted as a general matter, the result will be a tremendous expansion of international duties, but all in the service of international law.

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