[Southack]

Article VI
... This Constitution, and the laws of the United States which shall be made in pursuance thereof; and all treaties made, or which shall be made, under the authority of the United States, shall be the supreme law of the land; and the judges in every state shall be bound thereby, anything in the Constitution or laws of any State to the contrary notwithstanding.

[steve-b]

under the authority of the United States

Well, there you have it. A treaty which purports to authorize the government to behave un-Constitutionally is not made under the authority of the United States, because it is impossible by definition for an un-Constitutional act to be contained within that authority.