Certainly, under settled U.S. law, any subsequent treaty or domestic law can supercede a prior treaty (contrary to customary international law). But, if the Treaty was ratified by the Senate, the general rule is that the President has to faithfully carry out the laws and treaties of the United States, a general rule that would not ordinarily be met by the President simply declaring a treaty abrogated if the treaty doesn’t expressly give him that right (and this one does not). (The ABM Treaty which GWB withdrew the U.S. from was different because it expressly contemplated and provided for procedure for a nation’s withdrawal from the treaty).

Thus, this may be more of a separation of powers issue than it is an issue of the terms of the treaty (which U.S. law clearly gives Congress the power to abrogate even if the treaty by its terms forbids such action).