Article 72 Vienna Convention on Consular Relations
Non-discrimination
1.In the application of the provisions of the present Convention the receiving State shall not discriminate as between States.
2.However, discrimination shall not be regarded as taking place:
(a) where the receiving State applies any of the provisions of the present Convention restrictively because of a restrictive application of that provision to its consular posts in the sending State;
(b) where by custom or agreement States extend to each other more favourable treatment than is required by the provisions of the present Convention.
See also: Article 71 Vienna Convention on Consular Relations