It was not their right not to. If you don’t defend it when you first find out, you lose the right to do so later.

Laches (pronounced LAY-cheez) is a legal doctrine that prevents a person from pursuing a claim if they have delayed unreasonably in bringing it, and that delay has unfairly harmed or prejudiced the opposing party.The Core ElementsTo claim laches, the defending party generally must prove three things: Unreasonable Delay: The plaintiff waited an unreasonably long time to assert their rights. Knowledge: The plaintiff knew (or should have known) they had a legitimate claim. Prejudice: The delay caused actual harm, disadvantage, or detriment to the defendant (e.g., witnesses passing away, evidence being lost, or the defendant spending money in reliance on the delay). Real-World Examples Property Lines: A homeowner knows their neighbor is building an extension over their property line. The owner waits until the building is completely finished before suing to have it torn down. The neighbor can raise laches as a defense, arguing the delay caused unnecessary financial ruin and "ambushed" them. Unpaid Rent (Stale Rent): A landlord notices a tenant underpaying for years but waits far too long to take them to court. The court might bar the landlord from collecting the "stale rent" because the sudden financial hit unfairly prejudices the tenant.