Article 67 Vienna Convention on the Law of Treaties

Instruments for declaring invalid, terminating, withdrawing from or suspending the operation of a treaty

1. The notification provided for under article 65, paragraph 1, must be made in writing.

2. Any act of declaring invalid, terminating, withdrawing from or suspending the operation of a treaty pursuant to the provisions of the treaty or of paragraphs 2 or 3 of article 65 shall be carried out through an instrument communicated to the other parties. If the instrument is not signed by the Head of State, Head of Government or Minister for Foreign Affairs, the representative of the State communicating it may be called upon to produce full powers.

See also: Article 66 Vienna Convention on the Law of Treaties