The Vienna Treaty did not supercede the ratification requirements of the Constitution, period. Most other nations join a treaty when their chief executive signs it. But we do not, and the Vienna treaty did not change the very structure of the constitution.
Our Republican structure requiring Senatorial assent to the Presidents signature is still firmly in place. The rest of the world, and despotic Presidents, love to imagine that a Presidential signature binds us as it does most nations, but it certainly doesn’t.
Such authority! Uh, that would be "supersede."
In law, the Vienna Convention on the Law of Treaties has no authority because it was never ratified. In effect, it definitely has authority, else the Senate would not have held a "sense of the Senate" vote on Kyoto in order to give cover to those who could not be seen to support it without officially rejecting it. Nor would Bush II have "unsigned" the ICC Treaty, as Clinton's signature would otherwise have no effect. The government has been dancing around it for decades. It's a fact.
The signature means something until a conservative President can get hold of the Department of State and stage a nice layoff. BTW, no less an authority than Henry Lamb (may he rest in peace) did not know that the Vienna Convention had not been ratified because of the degree to which its terms have been integrated into the fabric of international law.
The rest of the world, and despotic Presidents, love to imagine that a Presidential signature binds us as it does most nations, but it certainly doesn’t.
Hand-wave noted on the strength of said august authority. It's been respected for forty years as "customary international law." Given that, until conservatives have a solid hand on both the Senate and the SCOTUS, I don't foresee any substantive change in the government's propensity toward treasonous usurpations of power.