Estopp

Estopp is a principle in common law that prevents a party from asserting a claim or right that is contrary to their previous conduct, representations, or statements when others have relied on them to their detriment. The core idea is fairness: it would be unjust to permit a party to contradict what they previously said or did after others have acted on that information.

Estoppel can arise in several forms. Estoppel by representation occurs when one party makes a false statement of fact or law to another, who relies on it in taking action or refraining from action; the party who made the statement cannot later deny its truth if doing so would harm the reliance that occurred. Promissory estoppel, often invoked in contract-like situations without consideration, prevents a party from going back on a promise if another person has relied on it to their detriment and it would be unjust to allow reversal. Estoppel by conduct, also called estoppel by implication in some contexts, arises when a person's actions or omissions lead others to believe a certain state of affairs and to act accordingly. Estoppel by deed binds a person to the facts, statements, or covenants contained in a deed, prohibiting later contradiction.

Estoppel is not a standalone cause of action; rather, it serves as an equitable defense or remedy to prevent injustice. Requirements typically include a clear representation or conduct, actual or reasonable reliance, and resulting detriment. The doctrine interacts with contract, property, and equity, and courts may exercise discretion in applying it based on the circumstances and public policy.