The agreement applies only to contracts concluded after its creation and to contracts between states and therefore does not regulate agreements between states and international organizations or between international organisations themselves, but if one of their rules is binding on these organisations, they will remain so.  The VCLT applies to interstate contracts within an intergovernmental organization.  However, agreements between states and international organizations or between international organizations themselves are governed by the 1986 Vienna Convention on treaty law between states and international organizations or between international organizations when it enters into force. Moreover, in treaties between states and international organizations, the provisions of the Convention continue to apply between states.  The convention does not apply to unwritten agreements.  During the history of sovereign states, diplomats enjoy a special status. Their function of negotiating agreements between states requires certain special privileges. An emissary from another nation is traditionally treated as a guest, his communication with his homeland is considered confidential and his freedom of coercion and submission by the host country is considered essential. The Vienna Convention on Consular Relations is an international treaty that establishes a framework for consular relations between sovereign states.
It codifies many consular practices stemming from state practices and various bilateral agreements between states.  The general objective of these international conventions and agreements, of which the Secretary-General of the United Nations is a custodian, is to facilitate international transport while ensuring a high level of security and environmental protection in transport: the Convention codifies several foundations of contemporary international law. It defines a treaty as “an international agreement that is written and governed by international law between states” and asserts that “every state has the capacity to conclude treaties.” Article 1 limits the application of the convention to written contracts between states, with the exception of treaties between states and international organizations or international organizations themselves. Article 26 defines pacta sunt servanda, article 53 proclaims the mandatory standard, and Article 62 proclaims a fundamental change in circumstances.