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Vienna Convention on the Law of Treaties

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By Tashmayee Sarkhel

Publication at: 03rd August, 2022 at 21:54 IST

The article includes the aspects of meaning, content, effects, scope, and signatories to the convention, Vienna formula, and interpretation of treaties about the Vienna Convention on the Law of treaties[1].

The Vienna Convention on the Law of Treaties (VCLT) is stated as an international agreement that regulates treaties between states. It is also known as the “treaty on treaties”. It is considered to be the cataloging or arrangement of customary international law and state practice concerning treaties.

The base of VCLT (Vienna Convention on the Law of Treaties) is built on the fulfillment of international commitments thereby giving reasonable guidance to the procedures for negotiating, interpreting, and applying international treaties and the rules for their compliance.

International agreement:

They are the formal understanding between two or more countries. Agreements between two parties are known to be “bilateral”, on the other hand, the agreements between several countries are known as “multilateral” and the countries who are bounded by an international agreement are referred to as “state parties.”

A Treaty can be called a convention, a protocol, a pact, an accord, and many more. The content of any of the agreements decides whether it is a treaty or not.

Then the 1969 Vienna Convention on the Law of Treaties has defined a treaty which is a typical instrument of international relations as an “agreement concluded between States in written form and governed by international law, whether embodied in a single instrument or into or more related instruments and whatever it’s particular designation. Contractual treaties are treaties by which the parties exchange pieces of territory or settle a dispute or claims that is, by which they deal with a particular kind of business. Law-making treaties, which have grown tremendously in number and significance during World War 2 are instruments in which the parties formulate principles or detailed rules for their future conduct.”

They help in avoiding costs and delays associated with inconsistent policies. There are even important determinants of global environmental health, trade agreements, and other international organizations and structures. On the main basis, they have become an important source of law which means that they can be the legal basis for regulating international economic relations, or they can be used for resolving certain disputes that may arise in concrete international economic relations.

History of VCLT:

The convention was adopted and signed on 23rd May 1969 and came into force on 27th January 1980. It was ratified in January 2018 by 116 States, while some non-ratifying parties like the United States, have recognized a few parts of it as a rewording of customary international law and binding upon them.

The VCLT is considered to be one of the most important instruments in treaty law and becomes an authoritative guide in disputes over treaty interpretation. It concisely represents the indexing of customary international law. It applies only to the treaties between the states.

The Vienna Convention on Law of Treaties was drafted by the International Law Commission (ILC) of the United Nations. The United Nations started working on the convention in the year 1949. The preparation of the convention took 20 years, in between which several draft versions of the convention and commentaries were prepared by the special rapporteurs (it is the title given to the individuals who work on behalf of the United Nations (UN) within the scope of “special procedure” mechanisms who have a specific country on a thematic mandate from the United Nations Human Rights Council) of the ILC. The special rapporteurs included eminent international law scholars like James Brierly, Hersch Lauterpacht, Gerald Fitzmaurice, and Humphrey Waldock. The ILC took up 75 draft articles in 1966 which led to the final work of the convention. Two sessions were held in 1968 and 1969 respectively, following which the Vienna Convention completed it and was adopted on 22nd May 1969 and was opened to receive signatories from the next days.

Content and effects of VCLT:

It codifies several substrata of contemporary International law (it is a set of Fundamentals and norms elaborated for the regulation of international relations between states and other entities that, within the International Law, are recognized as subjects of law). Definition of a treaty is done under it as “an international agreement concluded between States in written form and governed by international law”, and even pronounce that, “every state possesses the capacity to conclude treaties.”

A few articles under it are,

  • Article 1Restricts the application of the convention to written treaties between States, excluding treaties concluded between the states and international organizations or international organizations themselves[2].
  • Article 26 – It defines pacta sunt servanda (it is the Latin word for an “agreement must be kept” and is a fundamental principle of law)[3].
  • Article 53 – It demonstrates peremptory norm (it is a fundamental principle of international law that is accepted by the international community of a state as of norm from which no derogation is permitted)[4].
  • Article 62 – Proclaims about Fundamental Change of Circumstances (also known as clausula rebus sic stantibus, is the legal doctrine allowing for a contract or a treaty to become inapplicable because of a fundamental change of circumstances)[5].

Scope of VCLT:

The Convention only applies to treaties signed after it was written and to treaties between states; it does not apply to agreements between States and International organizations or agreements between international organizations themselves; however, any of its rules are independently binding on such organizations remain so. Treaties between nations within an Intergovernmental body are covered under the VCLT. If it enters into force, the 1986 Vienna Convention on the Law of Treaties between States and International Organizations or between International Organizations governs agreements between states and international organizations or between international organizations themselves. Furthermore, the terms of the Convention remain to apply between state members in treaties between states and international organizations. Unwritten agreements are not covered under the Convention.

Signatories to VCLT:

Till January 2018, 116 states had ratified the convention, with another 15 signed but not ratified it. Furthermore, the Republic of China (Taiwan), which is currently recognized by just 13 UN member states, signed the Convention in 1970, before the UN General Assembly voted in 1971 to transfer China’s seat to the People’s Republic of China, which later acceded to it. The convention has yet to be signed or ratified by 66 UN member states.

Vienna Formula about VCLT:

International treaties and conventions have regulations governing who can sign, ratify, or join them. Some treaties are only binding on states that are UN members or signatories to the International Court of Justice Statute. There is an explicit list of entities to which the treaty is restricted in unusual situations. More typically, the negotiating states’ goal (which is normal to have most or all of them become founding signatories) is to have the treaty not be limited to specific states, therefore language like “this treaty is open for signature to States willing to accept its contents” is used (the “all states formula”). In the case of regional organizations like the Council of Europe or the Organization of American Governments, the list of negotiating states that can sign and ratify a treaty once it is agreed upon is normally limited to its member states, with non-member states having the option to join later. Non-member nations or non-state actors may, on occasion, be invited to participate in discussions.

As a negotiating state, signing and ratifying a treaty has the same impact as a state acceding to a treaty (or “acceding a treaty”) that was not involved in its negotiation. Accession usually occurs after the treaty has entered into force, however, the UN Secretary-General General has occasionally allowed accession before the treaty has entered into force. The sole disadvantage of not being a negotiating state is that you have no say over the contents of a treaty, but you can still express objections about specific aspects of the treaty you want to join (Article 19)[6].

It may be difficult or impossible for the depositary authority to determine which entities are States when a treaty is available to “States.” When entities that appeared to be States could not be admitted to the United Nations or become Parties to the Statute of the International Court of Justice because of political opposition from a permanent member of the Security Council or because they had not applied for ICJ or UN membership, a problem arose regarding possible participation in treaties. Since that problem did not arise when it came to participation in specialized agencies, where there is no “veto” procedure, a number of those States joined specialized agencies and were thus recognized as states by the UN. The problem did not arise when it came to participation in specialized agencies, where there is no “veto” procedure, a number of those States joined specialized agencies and were therefore recognized as States by the international community. As a result, numerous conferences provided that they were also open to States members of specialized agencies, to order to allow for as wide a participation as feasible. The “Vienna formula” was named after the sort of entry-into-force phrase used in the Vienna Convention on the Law of Treaties, and its language was adopted by various treaties, conventions, and organizations.

Interpretation of treaties under VCLT:

  • Articles 31-33– The VCLT contains guidelines for interpreting conventions, treaties, and other agreements. The International Law Commission, for example, recognizes these concepts as embodying customary international law (ILC). Article 31’s interpretational principles must be applied before using those of Article 32, which expressly indicates that it provides additional possibilities for interpretation[7].
  • In investment arbitration cases, the VCLT is frequently used.


The crux importance of VCLT could be simply understood by it establishing detailed rules, methods, and standards for the definition, drafting, amendment, interpretation, and general operation of treaties. It even lays down a comprehensive framework for the establishment, maintenance, and termination of diplomatic relations between independent sovereign states based on mutual consent.

Perhaps the most successful international treaties in history are the Vienna Convention for the Protection of the Ozone Layer and the Montreal Protocol on Substances that Deplete the Ozone Layer. In reality, both agreements have the highest number of ratifications in United Nations history.

Hence, knowing the uttermost importance of international law in this growing world, the Vienna Convention on the Law of Treaties stands out to be one of the most important conventions among all the conventions listed under the International Law.

  1. The Vienna Convention on Law of Treaties, 1969
  2. The Vienna Convention on Law of Treaties, 1969, a.1
  3. The Vienna Convention on Law of Treaties, 1969, a.26
  4. The Vienna Convention on Law of Treaties, 1969, a.53
  5. The Vienna Convention on Law of Treaties, 1969, a.62
  6. The Vienna Convention on Law of Treaties, a.19
  7. The Vienna Convention on Law of Treaties, 1969, a.31,32 and 33