Doctrine of "Pacta Sunt Servanda"

International Law:

It is a doctrine borrowed from the Roman and its Latin meaning is "agreement must be kept"

It has been adopted as a basic principle for governing treaties in international law. Article-26 of the Vienna Convention on the law of Treaties says,

"every treaty in force is binding upon the parties to it and must be performed by them in good faith"
this is known as 'Pacta Sunt Servanda'

The theory is one sided for many usages and customary rules of international law on states apart from any agreement.
Anzilotti regard,

 "the doctrine Pacta Sunt Servanda is the basis of the binding force of international law".

 Many writers classify the maxim "Pacta Sunt Servanda" as a general principle of law, but it is in any event not to be doubted that the rule has all characteristics of a customary rule.