Equitable estoppel, sometimes referred to as estoppel in pais, is a legal doctrine which protects one party from the voluntary, harmful actions of another party. The concept is based upon assuring fairness to those who have relied upon the actions, either passive or overt, of another person or entity. Such actions include statements of fact, contractual assertions, a refusal to act in a timely manner, acquiescence, concealing facts and silence. Equitable estoppel also prevents a party from denying facts in subsequent legal actions which have already been previously established in a court of law.
The argument for equitable estoppel is generally raised in civil proceedings. One such area is in the issue of paternity, child support and custody suits. For example, Susan and John may have been married for five years, during which time a daughter is born. Susan has been secretly involved with Sam, one of her co-workers, and believes him to be the father of her child. She remains quiet about this possibility, however, and lists John as the father on the child’s birth certificate. John and his daughter develop a close, loving relationship.
Eventually Susan files for divorce so she can marry Sam. The court awards joint custody and requires John to pay child support. Later, Susan files a petition in court to strip John of parental rights, claiming that he is not the father of the child. In this case, the doctrine of equitable estoppel can be used to deny Susan’s petition. John can successfully insist upon his parental rights based upon Susan’s earlier acquiescence regarding his paternity and her overt actions of listing John as the father on the birth certificate and seeking child support at the time of the divorce.
Equitable estoppel is also used to prevent a party from making contradictory claims in a court of law. If a party sues someone for actions which have caused harm, he cannot later file a different claim for the same harm against a totally unrelated party. For example, a teacher who is dismissed wins a wrongful discharge suit against the school principal and a co-worker claiming he was fired as a result of discrimination. Later he may file a suit against a neighbor, claiming that the neighbor harassed the school and defamed his character, causing him to lose his job. He can be prevented from pursuing the second lawsuit since those claims contradict his testimony in the first lawsuit.
Promissory estoppel is a form of equitable estoppel which applies to contract law. This is most frequently used to force an entity to complete a contract when failure to do so can cause significant harm to the other party. For example, a large firm orders a significant quantity of material from a small chemical company. In order to meet the contractual deadline, the chemical company invests in additional equipment and supplies and turns away other customers. If the purchaser refuses to complete the purchase, the supplier can file a petition requesting the court enforce the contract under promissory estoppel.