pacta sunt servanda

Latin plural of pactum (“pact”) + sunt servanda (“must be kept”), after pacta et promissa semperne servanda sint (“whether agreements and promises should always be kept”) in Cicero, De Oficiis 3.92.

pacta sunt servanda

1. (law) Agreements must be kept. [from 19th c.]
   • 2004, FA Engelen, Interpretation of Tax Treaties under International Law, page 125:

     In the law of treaties, the most important manifestation of the principle of good faith is undoubtedly the rule of pacta sunt servanda.

   • 2015, Susan Pedersen, ‘At least we worried’, London Review of Books, volume 37, number 12:

     Painstakingly negotiated agreements governed many aspects of international relations; the doctrine of pacta sunt servanda dictated that those agreements be obeyed.

• a promise is a promise