The Shadow of Sanctions on Contracts

A valid contract is binding upon the parties. This statement serves as the cornerstone of contract law worldwide. However, it does not imply that there are no situations in which parties can legally terminate, suspend, or refuse to fulfill their contractual obligations for legal reasons. Typically, these reasons can be anticipated ex-ante in applicable law or in the contract itself. How about newly introduced sanctions? Can they provide a green light for parties to refrain from undertaking their contractual obligations?