Article XV provides that reservations cannot be taken to the Articles of and Annexes to the Treaty. The Article further provides that reservations cannot be taken to the provisions of the Protocol to the Treaty and the Annexes to the Protocol that are incompatible with the object and purpose of the Treaty. Note that in allowing reservations to the Protocol and Annexes to the Protocol, Article XV repeats the requirements of Article 19(c) of the Vienna Convention on the Law of Treaties, i.e., a state may formulate a reservation to a treaty unless the reservation is incompatible with the object and purpose of the treaty. The U.S. is not a party to the Vienna Convention on the Law of Treaties. However, the U.S. views parts of the Vienna Convention on the Law of Treaties as declarative of customary international law.
It is recognized that in its resolution of advice and consent to ratification of the Chemical Weapons Convention, the Senate adopted a binding condition accepted by the President that required the President to certify to Congress that the United States had informed all other States Parties to the Convention that the Senate reserved the right, pursuant to the U.S. Constitution, to give its advice and consent to ratification of the Convention subject to reservations, notwithstanding Article XXII of the Convention, which prohibited reservations to articles of the Treaty. On April 25, 1997, President Clinton certified to Congress that all other States Parties had been so informed. The intent of the prohibition on reservations in Article XV of the CTBT is to constrain irresponsible behavior by states that might seek to undermine the effect of the Treaty and to promote certainty for others. The Senate retains the right to express its views on all provisions of the Treaty and to impose conditions, consistent with the U.S. Constitution, in connection with Executive Branch ratification of the Treaty. However, if such conditions included a reservation to the Treaty, the United States would be unable to ratify it.