What doctrine states that if a property owner is lax in protecting his or her rights, the property owner may lose those rights?

The doctrine of laches

Explanation:

The doctrine of laches is a defense in court that can be asserted in a civil case, claiming that there has been an excessive delay in implementing the request, which has biased the defendant, or prevented him from pursuing a defense.

If the proprietor does not respond in a timely way to an illegal structure based on an act of limitation and waits for the complete construction of the structure, the judge may apply this law.