The Supreme Court on the Treaty Power:
The President has the "Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two thirds of the Senators present concur" (U.S. Const., art. II, sec. 2, cl. 2.) The treaties then become the "supreme Law of the Land" (art. VI), and Congress may enact legislation that is necessary and proper for complying with the treaties (art. I, sec. 8). Does this include only those treaties that cover subjects within the federal government's other enumerated powers (for instance, over warmaking, foreign commerce, and the like)? Or does this also include treaties that deal with subjects that would otherwise (but for the Treaty Power) be outside the federal government's powers?

     For instance, the Supreme Court has struck down the Religious Freedom Restoration Act, as applied to the states, on the grounds that it exceeds the federal government's enumerated powers -- if the President signs a treaty mandating all signatories to exempt religious objectors from many generally applicable laws, the Senate ratifies the treaty, and Congress reenacts RFRA to implement the treaty, would that be constitutional? (Some people argue that our human rights treaty obligations already provide an authority for such a statute, but I'm skeptical.)

     The question isn't whether the Treaty Power can trump the Bill of Rights and other individual rights protections can't be trumped by treaty; it's pretty well-established that it can't. Rather, the question is whether it provides an independent source for federal power, or whether it's governed by the article I limitations on federal power as well as by the individual rights limitations.

     The Supreme Court's answer to this, delivered in Missouri v. Holland (1920), is that the Treaty Power is an independent power. A Religious Freedom Restoration Act-enabling treaty could indeed let Congress do what, absent a treaty, it couldn't have done. Nonetheless, people have hotly debated whether this is right, and in recent years there has been some talk that the conservative Justices on the Court, who have tried to in some measure restrain federal power, could overturn or limit Missouri v. Holland.

     Today's decision in United States v. Lara seems to suggest that Chief Justice Rehnquist and Justice O'Connor, at least, continue to endorse Missouri v. Holland. In the course of dealing with a rather different question related to the Indian tribes' inherent powers, the Court gave the Treaty Power as one source of authority for Congress to "legislate in respect to Indian tribes," and in the process said (some citations omitted):
The treaty power does not literally authorize Congress to act legislatively, for it is an Article II power authorizing the President, not Congress, "to make Treaties." But, as Justice Holmes pointed out, treaties made pursuant to that power can authorize Congress to deal with "matters" with which otherwise "Congress could not deal." Missouri v. Holland, 252 U. S. 416, 433 (1920); see also L. Henkin, Foreign Affairs and the U. S. Constitution 72 (2d ed. 1996). And for much of the Nation's history, treaties, and legislation made pursuant to those treaties, governed relations between the Federal Government and the Indian tribes.
This was written by Justice Breyer, but Rehnquist and O'Connor joined this section without reservation; and those who didn't join -- Justices Scalia, Kennedy, Souter, and Thomas -- didn't express any opposition, either.

     It may well be that if the question is more squarely presented, Rehnquist and O'Connor might take a different view -- but I doubt it, since they were certainly free to express their reservations in this case, and still join the rest of the opinion. And even if Rehnquist and O'Connor retire in the next several years, the fact that these two conservatives, who have long spearheaded the attempt to limit federal power in some measure, endorse Missouri v. Holland suggests that even conservative replacements for them might take a similar view.