Is It Unlawful to Breach a Treaty?

Is It Unlawful to Breach a Treaty?

A while back, Marty Lederman had posted a comment asking some probing questions on my post on the legality of the current Iraq War and on the bombing of Serbia by NATO during the Kosovo conflict (both available here). While a variety of other issues have come up in the last week, I didn’t want to let his questions go unanswered.

I want to start with the end of Marty’s comment, which focuses on the main question he had about my post:

Because there are serious ramifications for breach of a treaty, we ought to enact breaching legislation only rarely, and only after very solemn and careful deliberation. And in accord with the Charming Betsy canon, statutes should be construed, wherever possible, to be consistent with U.S. treaty obligations. But in what sense is a treaty-breaching statute illegal under U.S. law — including the Supremacy Clause?

Actually, I think Marty and I are basically in agreement: I am not arguing that a later statute that would cause a treaty breach would be illegal under U.S. law; I only argue that U.S. actions breaching a treaty would be illegal under international law.

Marty describes the situation in this way:

Congress *often* enacts “last in time” statutes that effectively violate treaties, or that breach federal contracts, or that contradict earlier statutes. In many such cases the federal government must, of course, suffer the consequences of the change in law, such as (sometimes) paying for contract breaches, or suffering international sanctions, etc. But we rarely characterize the new statute as *unlawful* simply because it violates a previous promise that we have made.

If the hypothesized domestic statute caused a breach of international legal obligations under a previous treaty then, in the sphere of international law the U.S. is acting in a manner that would be unlawful. (I am assuming here that in passing the later statute the US did not denounce or terminate the treaty by accepted procedures.) Or, perhaps more technically, U.S. actions would give rise to a claim of state responsibility.

Marty described the situation as akin to a contract breach or to passing a later statute that trumps an earlier statute. I want to walk through some of the implications of these analogies in relation to the domestic and international roles of treaties.

The contract analogy has often been used to describe some treaties, such as certain types of trade agreements. Other treaties, due to their subject matter, complexity, and/or the rights and obligations they describe, are cosnsidered to be less like contracts and more like statutes (or even constitutions); consider the U.N. Charter or the WTO Agreements.

In the end, though, treaties aren’t contracts, or statutes, or constitutions. Treaties are their own species and the various analogies that we use to describe them are only useful up to the point that they obscure rather than enlighten. (If anyone wants to read more on treaty breaches and analogies to domestic texts such as statutes and contracts, I have an article entitled “Resolving Treaty Conflicts” coming out this Spring in the George Washington International Law Review on this topic.)

So while Marty says that the later statute may cause a contract breach (which is not illegal) or may simply supercede an earlier statute (which is not illegal domestically, it is merely a change in law), I don’t think either analogy is applicable in the international arena for the fact pattern we are discussing. By breaching a treaty, the U.S. isn’t merely breaking a contract. Domestic U.S. jurisprudence allows for parties to breach contracts without making such actions illegal because contracts are merely private methods for parties to order their affairs within the confines of an overarching legal system. Treaties, on the other hand, are recognized as a key source of law in the international legal system. While contracts are within a domestic legal system, treaties are a large part of the international legal system, itself. Thus, in domestic law, we accept the “efficient breach” of contracts (breaches that lead to economically efficient results), but in the international system, the default rule is pacta sunt servanda, “the agreement shall be observed.”

Similarly, while a later U.S. statute may simply supercede an earlier treaty for domestic purposes, this analogy breaks down when applied internationally. While the treaty is an instrument of international and possibly domestic law-making, the statute is an instrument of only domestic law-making. Thus, regardless of the domestic legal change caused by the later statute, at the international level we do not have a change of law but a unilateral breach giving rise to state responsibility.

So, in sum, a later domestic statute would countrol over an earlier treaty and be perfectly legal domestically. If, however, the U.S. is consequently breaching its international obligations, then the U.S. behavior would be seen as unlawful in regards to its international obligations.

(And, by the way, there’s a whole other set of issues concerning whether a breach would require actual state practice in contravention of a treaty–enforcing the later in time statute–or whether the mere act of enacting the statute (whose enforcement would be a breach) would itself be an anticipatory breach. If that interests you, I would refer you to my forthcoming article mentioned above…)

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Julian Ku
Julian Ku


Any thoughts on whether the U.S. could, consistent with international law, withdraw from the Vienna Convention’s Optional Protocol?

Marty Lederman
Marty Lederman

Thanks, Chris. Very interesting and informative.

As Julian suggests, we may be on the verge of a much more complicated *constitutional* question — namely, whether and under what circumstances a treaty continues to be the “supreme Law of the Land” after the President unilaterally (i.e., without Senate or congressional authorization) determines that the U.S. has “withdrawn” from the treaty.