self-help

Definition from Nolo’s Plain-English Law Dictionary

Obtaining relief or enforcing one's rights outside of the normal legal process. Examples include repossessing a car when payments have not been made, retrieving borrowed or stolen goods, demanding and receiving payment, or abating a nuisance (such as digging a ditch to divert flooding from someone else's property). Self-help is legal as long as it does not "break the public peace" or violate some other law (although brief trespass is common).

Definition provided by Nolo’s Plain-English Law Dictionary.