This chapter examines how a state becomes a party to a treaty, including signature, initialling and ratification, where applicable. Whether a state can participate in a multilateral treaty depends on the terms of the treaty. The practice of the Council of Europe is examined. Signature may express consent to be bound but often signature will be subject to ratification. Ratification is the international act whereby a state establishes on the international plane its consent to be bound. It is to be distinguished from the domestic process which enables a state to ratify. Advice is given on the form and content of an instrument of ratification. A state may also consent to be bound by acceptance, approval or accession. Accession is primarily the means by which a state may become a party if it is unable to sign the treaty. The chapter also examines rights and obligations prior to entry into force, the possibility of withdrawing consent to be bound, and the ways in which treaties might be developed.

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.

The chapter concerns steps to consider in preparing to become party to a treaty. It examines the eligibility of States and IOs to participate in multilateral treaties, including scenarios in which eligibility to join a treaty is not clear and what procedures may be used to resolve such issues. The chapter explains the importance of understanding ‘modes of expressing consent to be bound’, and choosing the appropriate mode. It looks at how a treaty may be made by exchange of instruments. Lastly, the chapter considers internal preparations to give consent to be bound for States and IOs, including consultations with stakeholders.