A treaty may be in the form of an agreement between the heads of states of the concerned countries, in an inter-governmental form, between ministers of the respective countries, or it may be an inter-departmental agreement.

• it should be embodied in a written instrument between two or more entities;

• those entities should be endowed with international personality;

• it should be governed by international law.

The making of treaties involves various steps, viz., consultation, negotiation and adoption of the text, commencement of treaty, ratification, accession, adhesion etc.

Full powers is a formal document emanating from the competent authority of a state designating a person or persons to represent the state for negotiating, adopting or authenticating the text of a treaty, for expressing the consent of the state to be bound by a treaty, or for accomplishing any other act with respect to a treaty.

Heads of states, heads of governments, ministers for foreign affairs, heads of diplomatic missions, and representatives accredited to international conferences or organizations are considered to represent the state ex officio (by virtue of their position). Therefore, they are empowered to sign a treaty on behalf of a state without having to produce full powers to that effect. 

Deferred signatures generally denotes that the negotiated text was not fully acceptable to the signatory state at the time of authentication; and moreover, they are without any legal effect unless confirmed subsequently by the state.

As a first step towards the conclusion of treaty is the negotiation and adoption of the text. Once the state decides to enter into a treaty relationship, it appoints the representatives to negotiate the text of the treaty. These representatives should be duly empowered through “full powers”.

A state may express its consent to be bound by a treaty by signature, exchange of instruments constituting a treaty, ratification, acceptance, approval or accession, or by any other means agreed between the parties.

Ratification is the international act whereby “a State establishes on the international plane its consent to be bound by a treaty” (Art. 2(1)/b, Vienna Convention). Ratification is an act of government to approve the treaty in question. Treaty becomes binding on the state after ratification. 

Accession, adhesion or adherence is a method by which a state becomes a party to a treaty of which it is not a signatory. Under the earlier practice, accession could be made only after the treaty had come into force. According to present practice, a non-signatory state may accede before or after the treaty has come into force.

Entry into force of a treaty is entirely dependent upon the agreement between negotiating States (Art. 24/1). They may prescribe the manner and the date for its coming into force. They may agree that the treaty shall be effective immediately after signature, or at some fixed time, i.e., 30, 60 or 90 days after the prescribed number of ratifications or accessions is deposited, or on the happening of a certain event.

A reservation is a unilateral statement made by a state at the time of signing, ratifying, accepting, approving or acceding to a treaty, whereby it purports to exclude or modify the legal effect of certain provisions of the treaty in their application to that state.

The rationale behind reservation is that a state which is unable to fulfill its treaty obligations in totality because of certain constraints should be allowed to do so, even if in a limited way, provided that the reservation does not materially affect the basic provisions of the treaty.

• A treaty becomes voidable in contravention of constitutional limitations;
• A state contesting the validity of a treaty on constitutional grounds may invoke only those provisions of the constitution which are notorious;

Treaties are liable to be terminated or suspended either in accordance with the will of the parties or by the operation of any rule of law.

• Textual (ordinary meaning of the words),

• The intention of the parties,

• Teleological (the object and purpose of the

  treaty).

Amendment is related to the individual provisions of a treaty, whereas revision concerns with the general review of the whole treaty.

• the modification in question is prohibitedby the treaty, or

• it affects the rights and obligations of other parties under the treaty, or

• it relates to a provision, derogation from which is incompatible with the effective execution of the object and purpose of thetreaty as a whole