International Judicial Monitor
Published by the American Society of International Law and the International Judicial Academy
September 2008 Issue

General Principles of International Law

Pacta Sunt Servanda

General Principles of International Law Are states really bound to fulfill the commitments they undertake pursuant to a bilateral or multilateral treaty once it has been ratified and then enters into force?  According to pacta sunt servanda, they are. This Latin phrase, which may be roughly translated as “treaties shall be complied with,” describes a significant general principle of international law—one that underlies the entire system of treaty-based relations between sovereign states.   

The duty to perform one’s solemn obligations is not something unique to international law and the law of treaties. A similar principle can be found in the contract law of many domestic legal traditions throughout the globe. Every agreement of a legal nature, domestic or international, whether it is a contract between individuals or a treaty between states, presupposes that in concluding the agreement the parties acted with the intention to abide by its provisions.      

State practice over the centuries has recognized the fundamental significance of pacta sunt servanda as a principle or rule of international law. What was originally an uncodified rule based on customary practice began to be expressed in writing in the mid-nineteenth and early twentieth centuries through multilateral declarations, such as the Declaration of London of 1871, and decisions of international arbitral bodies. It was also incorporated into the Covenant of the League of Nations and the Charter of the United Nations, although neither document referred to the principle by name.

Explicit reference to pacta sunt servanda in an international legal instrument was first made when drafting the Vienna Convention on the Law of Treaties of 1969 (VCLT).  This document, which is widely considered to be the most definitive authority on treaty law and practice, makes reference to pacta sunt servanda as a universal rule in its Preamble and also devotes a brief article to its definition.

Article 26 of the VCLT states, “[e]very treaty in force is binding upon the parties to it and must be performed by them in good faith.” 

The good faith element of this principle suggests that states should take the necessary steps to comply with the object and purpose of the treaty. States may not invoke restrictions imposed by domestic law as good reason for not complying with their treaty obligations provided the instrument was duly ratified by competent authorities and in accordance with constitutional and statutory requirements.

For more information on pacta sunt servanda and the law of treaties, please consult the following resources: 

Electronic Resource Guide:  Introduction to Treaty Research

International Law:  A Handbook for Judges

Max Planck Encyclopedia of International Law

Restatement of the Law Third:  Foreign Relations Law of the United States  

Andrew Solomon, Director of Programs, American Society of International Law


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Editors: James G. Apple, Veronica Onorevole and Andrew Solomon.
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