There is also the issue of the State Dept deciding that treaties which the President has signed, but have not yet been ratified, still need to be adhered to. There was some legislation or other negotiation recently where they insisted on honoring the terms of the Law of the Sea treaty, another which has been signed by a President but has not been ratified. This along with executive agreements are but two ways we can find ourselves living under the terms of such treaties without actually being legally bound to them.
Federal courts and the Supreme Court have also been flirting with the notion of folding international laws and "standards" into their decision making on various US cases (sodomy law cases, capital punishment cases, EPA and "clean air" related cases, etc.). While those that engage in such "thought experiments" will pronounce that such laws and standards are not driving their decisions on cases, that is cold comfort given the long history of judicial overreach, social engineering, the notion of the living constitution as espoused by the more liberal members of the bench, and the human desire to stand out and "make law" through the precedents they set. Perhaps such standards and international law have not played a deciding role in US jurisprudence so far, but it seems it is only a matter of time before the right balance of judgicial philosophy finds itself on the bench, emboldening them enough to take that last step to making certain legal practices and standards overseas the law of our land too.
I don't know if Monkton is right about the draft treaty for Copenhagen having provisions to establish a world government for environmental concerns (particularly as they relate to CO2 production), with powers of taxation and injunction and all the rest, but I don't doubt for a second it comes damn close to what he is warning about here or that it could very easily morph into what he warns of once signed or ratified. And there is much evidence to suggest we could find ourselves being held to the terms of this treaty even without formal ratification.