When the doctrine of promissory estoppel is applied, the promisor is estopped, or barred, from performing the promise.

Promissory Estoppel

A doctrine that applies when a promisor makes a clear and definite promise on which the promisee justifiably relies. Such a promise is binding if justice will be better served by the enforcement of the promise.

Promisor

An individual or entity that makes a promise to perform an act or fulfill an obligation as specified in a contract.