Impossibility of performance

The doctrine or principle of impossibility, impossibility of performance or impossibility of performance of contract is a doctrine in contract law, and in this context, the "impossibility defense" is a defense offered against a claim for nonperformance. In contract law, impossibility is an excuse for the nonperformance of duties under a contract, based on a change in circumstances (or the discovery of preexisting circumstances), the nonoccurrence of which was an underlying assumption of the contract, that makes performance of the contract literally impossible.

Source: Wikipedia — Impossibility of performance (CC BY-SA 4.0)