What does estoppel prevent a party from doing?

Estoppel is a legal principle that prevents a party from asserting a claim or right that contradicts what they have previously established as true, especially when that previous position has been relied upon by others. In the context of waiving a right, if a party has voluntarily relinquished a known right or claim, estoppel prevents them from later asserting that right again. This principle is crucial in maintaining fairness and stability in legal and contractual relationships, ensuring that parties cannot backtrack on their agreements or acknowledgments to the detriment of others who have relied on their prior conduct.

In short, when someone waives a right, estoppel ensures that they cannot return to that right without adequate justification, thus preserving trust and preventing unfair surprise in legal proceedings or contractual engagements.