The Treaty Paradox

[J. J.]

The Slave Trade Clause, by its own terms, applies only to Congress. The clause does not, therefore, restrict the President's treaty-making power. Nevertheless, I would hold that a treaty purporting to prohibit individuals from engaging in the slave trade would be unconstitutional, or at the very least non-self-executing.

The power to "regulate Commerce with foreign Nations" is expressly vested in Congress by Art. I, Sec. 8, Cl. 3. Furthermore, the regulation of international commerce is very clearly a "legislative power," and "all legislative powers" are vested in Congress by Art. I, Sec. 1. I would argue that, if a power is vested in Congress, then the President may not exercise that same power, by ratifying a treaty or otherwise. Thus, a treaty may not prohibit the slave trade (since such a prohibition is a regulation of international commerce).

Whether any treaty at all can be self-executing is a very difficult question. The answer is not immediately clear from the text of the Constitution. I'll try to make another post on the subject sometime soon.

I think this might have some bearing on the subject:  http://en.wikipedia.org/wiki/Moors_Sundry_Act_of_1790#cite_note-0

The SC state legislature found that a freeborn citizen of an allied nation could not be subject the "Negro Laws" even if they happened to be black.

In looking at the Federalist 64, treaties seem to be elevated to a level equal to the Constitution, a treaty that said countries could not engage in the slave trade, or a treaty saying that no county shall permit slavery, would be constitutional.

[J. J.]

The SC state legislature found that a freeborn citizen of an allied nation could not be subject the "Negro Laws" even if they happened to be black.

How is this law relevant to my claim that the treaty-making power cannot overlap with the legislative power of Congress?

It show that a state legislature, one that, a few years later, was willing to nullify federal statute, would recognize the primacy of a treaty between the US and foreign power.

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The constitution requirement for a treaty has been met.  As you have pointed out, the clause only applies to Congress making a statute, not to the Senate approving a treaty.  Even in the context of the time, that distinction seems to have been recognized.

[J. J.]

It show that a state legislature, one that, a few years later, was willing to nullify federal statute, would recognize the primacy of a treaty between the US and foreign power.

I definitely agree that a treaty supersedes state law. There is no need to cite historical events; the text of the Constitution is clear enough to resolve the issue. Under the supremacy clause, treaties made under the authority of the United States are the supreme law of the land, any state law to the contrary notwithstanding.

But this discussion is not about whether valid treaties trump state law. The dispute is about whether a particular treaty--a treaty purporting to abolish the slave trade--is valid in the first place. If it is valid, then state laws to the contrary are void, but it must first be established that the treaty is constitutional.

Clearly, there must be some limits to the treaty power, beyond the requirement that the Senate advise and consent by a two-thirds majority. Could a treaty impose taxes, or regulate the jurisdiction of the Supreme Court, or appropriate funds from the Treasury? I would think not. The power to abolish the slave trade, and the power to regulate international commerce more generally, is of the same ilk -- it is delegated to Congress, not the President.

We've seen some proposed treaties, e.g. ones relating to war crimes, that have not been ratified because they could permit US armed forces members to be tried by non US courts. 

I think a treaty banning the slave trade could have been constitutionally ratified and be in force.