Article 46 Vienna Convention on the Law of Treaties

Provisions of internal law regarding competence to conclude treaties

1. A State may not invoke the fact that its consent to be bound by a treaty has been expressed in violation of a provision of its internal law regarding competence to conclude treaties as invalidating its consent unless that violation was manifest and concerned a rule of its internal law of fundamental importance.

2. A violation is manifest if it would be objectively evident to any State conducting itself in the matter in accordance with normal practice and in good faith.

See also: Article 45 Vienna Convention on the Law of Treaties