Wiener Übereinkommen über das Recht der Verträge
Article 27 of the Vienna Convention on the Law of Treaties from 1969 provides that if a treaty conflicts with a state's municipal law (including the state's constitution), the state is still obliged to meet its obligations under the treaty. The only exception is provided by Article 46 of the Vienna Convention if a state's expression of consent to be bound by a treaty was a manifest violation of a "rule of its internal law of fundamental importance".