Estoppel is a legal principle that prevents a person or entity from asserting a legal right or taking a legal position that contradicts or is inconsistent with its earlier position, behavior, or agreement. The person or entity is said to be “estopped” from changing its position, behavior, or agreement because another person or entity has relied on its earlier position, behavior, or agreement (detrimental reliance).

In California, estoppel is a legal doctrine that is used to bar a party from adopting a position in a legal proceeding that is contrary to their previous stance if the other party has relied on the original position to their detriment. This principle is applied across various areas of law, including contract law, property law, and family law, to promote fairness and prevent injustice. Estoppel can take several forms, such as promissory estoppel, equitable estoppel, and estoppel by deed. For instance, promissory estoppel occurs when a party makes a promise that another party relies upon, and even in the absence of a formal contract, the promisor may be prevented from reneging on the promise. California courts will consider factors such as the representation made by the estopped party, the reasonable reliance by the other party, and the detriment suffered as a result of the reliance. The specific application of estoppel principles can vary depending on the facts of each case, and an attorney can provide guidance on how estoppel might apply in a particular legal situation.