(a) Heads of State, Heads of Government and Ministers for Foreign Affairs, for the purpose of

performing all acts relating to the conclusion of a treaty;

(b) heads of diplomatic missions, for the purpose of adopting the text of a treaty between the

accrediting State and the State to which they are accredited;

(c) representatives accredited by States to an international conference or to an international

organization or one of its organs, for the purpose of adopting the text of a treaty in that conference, organization, or organ.

(article 7(2) of VCLT)