On the recordMay 14, 1997
Article II of the Constitution gave the President and the Senate equal treaty making powers, stating that the President ``shall have the power, by and with the Advice and Consent of the Senate, to make Treaties, provided two thirds of the Senators present concur.'' Substantive changes to treaties also require the advice and consent of the Senate. John Jay made one of the most persuasive arguments about this point, noting that, ``of course, treaties could be amended, but let us not forget that treaties are made not by only one of the contracting parties, but by both, and consequently that as the consent of both was essential to their formation at first, so must it ever afterwards be to alter . . . them.'' Condition 9 of the resolution of ratification for the CFE Flank Agreement protects the Senate's constitutional role by requiring that any agreement to multilateralize the 1972 ABM Treaty be submitted to the Senate for advice and consent, since any such agreement would substantively alter the rights and obligations of the United States and others under the treaty.
Source
govinfo.gov




