Paragraph 1 of Article XVI states that the Convention shall be of unlimited duration.
Paragraph 2 of Article XVI sets forth the conditions for withdrawal from the Convention. Specifically, this paragraph states that each State Party shall, in exercising its national sovereignty, have the right to withdraw from the Convention if it decides that extraordinary events, related to the subject matter of the Convention, have jeopardized the supreme interests of its country. This paragraph further states that a withdrawing State Party shall give notice of such withdrawal 90 days in advance to all other States Parties, the Executive Council, the Depositary and the United Nations Security Council. Finally, this paragraph states that such notice shall include a statement of the extraordinary events the withdrawing State Party regards as having jeopardized its supreme interests.
Note that this provision is virtually identical to those used in prior U.S. arms control agreements, e.g. Article XV of the Intermediate-Range Nuclear Forces Treaty and paragraph 3 of Article XVII of the Strategic Arms Reduction Treaty.
Paragraph 3 of Article XVI states that the withdrawal of a State Party from the Convention shall not in any way affect the duty of States to continue fulfilling the obligations assumed under any relevant rules of international law, particularly the Geneva Protocol of 1925. The purpose of this paragraph is to make clear that a State Party that withdraws from the Convention is, at a minimum, still prohibited, by customary international law and the Geneva Protocol, from the first use of chemical weapons in war. (The general relationship between the Convention and the General Protocol of 1925, as well as the Biological Weapons Convention, is discussed in Article XIII.)