Wiener Übereinkommen über das Recht der Verträge
When the two parties in a bilateral treaty are two countries bound in an international agreement, they are generally referred to as "state parties". The nature of an agreement between two state parties is subject to rules dictated by the Vienna Convention on the Law of Treaties. An agreement between a state or organization and an international organization is subjected to the rules defined by the Vienna Convention on the Law of Treaties between States and International Organizations or between International Organizations.