Normally, treaties contain express provision on duration and termination. These can take a variety of forms, including indefinite duration with a right to terminate, or a conditional right to terminate. Various types of clauses are examined, together with the situation where a treaty contains no provision for termination or withdrawal. A treaty may also be terminated by consent or by conclusion of a later treaty. The chapter examines the relationship between treaty provisions and countermeasures, and analyses the right of one or more parties to terminate or suspend a treaty for material breach. It also examines other grounds for termination, including supervening impossibility of performance and fundamental change of circumstances (rebus sic stantibus), the procedure for termination, and special circumstances such as the severance of diplomatic relations or outbreak of hostilities.

Chapter 6 deals with the final motion relating to a treaty, ie its destruction (phthora). To this effect, the chapter starts with an examination of withdrawal from a treaty, even when no such withdrawal clause exists, and the possibility of revocation of a notification of withdrawal. This last one rose to prominence with Brexit and the Wightman cases. The situation is further complicated by the fact that anomalous situations can also occur where termination or suspension may be required. Chapter 6 does not examine only the existing grounds of termination/suspension under the VCLT, but also certain grounds that despite not being included in the VCLT have been argued to provide additional, customary law-based grounds for termination/suspension. Two kinds of motion are examined in this context: i) the motion between the VCLT and non-VCLT alleged grounds for termination/suspension, ie the connections, near identity and in some cases suggested absorption of one ground by another; and ii) the motion between, on the one hand, the grounds for termination/suspension, as a subset of treaty law, and, on the other hand, other sets of rules such as State responsibility.