The laws of treaties are in constant motion and state of flux, which has different connotations. It relates to motion through time and also the manifestation (or lack thereof) of change. The basic principle of the definition of motion, adopted by the authors, is based on the philosophy of Aristotle. He identified six types of motion: creation (genesis), increase (auxesis), diminution (meiosis), alteration (alloiosis), destruction (phthora), and change of place (kata topon metabole). This last type of motion has been amended by the authors to change in space-time (kata topon kai chronon metavole) to reflect our modern scientific understanding of time as a dimension through which motion and change occurs.

This Chapter concerns the formation (genesis) of a treaty. It deals with the substantive and formal elements of a treaty, ie when international obligations emerge through a treaty, when is a treaty a treaty, and who is entitled to bind a State through a treaty. This Chapter examines numerous cases by international courts and tribunals relating to this subject matter. It also analyses the debate ssurrounding memoranda of understanding (MOUs), soft law and modern law-making, such as the Paris Agreement on Climate Change, which comprises hard and soft law obligations. Finally, it looks at the registration of a treaty, ie to what extent, if any at all, it contributes to its formation and identification.

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.

This chapter examines the notion of consent to be bound from the point of view of its motion and change from a classical concept included in the Vienna Convention on The Law of Treaties (VCLT), to its evolution in modern times. It also analyses the question of reservations to treaties, which was one of the projects of the International Law Commission. The chapter deals with the contentious issue of reservations to human rights treaties. The chapter also demonstrates that since consent to be bound is integral to the whole system of treaty law, it can also be identified in situations where we have an increase (auxesis), diminution (meiosis) or even alteration (alloiosis) of the treaty, as can happen when we are dealing with the system of reservations.

Chapter 5 on amendment, modification, and revision is organically linked with the former chapter on interpretation. It deals with the possibility of a temporal motion of a treaty through amendment, modification or revision. This may lead to either increase (auxesis), diminution (meiosis), or even alteration (alloiosis) of a treaty. The chapter goes through the development of the rules of amendment and modification in the VCLT, and also examines the contemporary development of the law of treaties through conferences of parties established by multilateral environmental agreements. This practice has led to new approaches to treaty modification, which did not exist in classical international law. It may be said that such modifications are effected through secondary legislation, which in turn may lead to the questions of legitimacy. This chapter concludes with an examination of the patterns of amendment and modification that emerge from the multilateral treaties that have been registered in the League of Nations and United Nations Treaty Series.

This chapters concludes and summarises the main analysis, research and findings presented in the previous chapters.

This chapter tackles the issue of interpretation from the point of view of motion and time, mainly motion as change in space-time (kata topon kai chronon metavole), which depending on the interpretation could lead to an increase (auxesis), diminution (meiosis) of the treaty. This is mainly evidenced through the concepts of the principle of contemporaneity and evolutionary interpretation, and the chapter proceeds to demonstrate that the choice between these two is dependent on the ‘time-will’ of the parties. However, even evolutive interpretation has its limits and should never lead to an alteration (alloiosis) of the treaty. This chapter also analyses the rules of interpretation themselves, ie whether interpretative rules are constants, immutable and perennial ones, in the system of the law of treaties or whether they are, as any other rule, potentially susceptible to motion through time and change. This chapter demonstrates the false premise of the immutability of the rules of interpretation, and elaborates on the consequences of this to the choice between contemporaneous (static) and evolutive interpretation.