Uh, according to Article II, Section 2, Clause, 2 of the Constitution, that would be by "two thirds of the Senators present," not the several States. But you have a bigger problem than that.
According to "customary international law" pursuant to the Vienna Convention on the Law of Treaties (which we never ratified), once it has been signed, the government has agreed not to contravene the treaty, the Constitution in effect notwithstanding. The government of the United States has abided by that treaty (illegally) ever since it went into effect.
So.... after Obozo signs it and it goes into effect.. Can we march on DC and burn it down?
We kind of want to anyway for all the OTHER crap they are doing. We running out of camel on which to pile straws...