What does estoppel prevent a party from doing?

Estoppel is a legal principle that prevents a party from asserting a right or privilege that they have previously waived or relinquished. In the context of the question, when a party has waived a right or privilege and established a reliance on that waiver—often to the detriment of another party—estoppel will prevent them from later asserting that right or privilege again. This concept is critical in ensuring fairness and integrity in contractual relationships, as it promotes reliance on the established actions and communications between the parties.

For example, if a party consistently acted in a manner that suggests they have waived a right (such as a right to contest a particular issue), they cannot later reclaim that right once the other party has relied on their behavior or representation in a way that would lead to unfairness if the right were reasserted.

In contrast, the other choices deal with concepts that do not accurately reflect the core function of estoppel, which primarily hinges on maintaining consistency in legal relationships and preventing inconsistency that can lead to unjust outcomes.