Just compensation is a right enshrined in the Fifth Amendment to the U.S. Constitution (and counterpart state constitutions), which is invoked whenever private property is taken (also in some states damaged) by the government. Usually, the government (condemnor) files an eminent domain action to take private property for "public use.", but when it fails to do so and pay for the taking, the owner may seek compensation in an action called "inverse condemnation." For reasons of expedience, courts have been generally using fair market value as the measure of just compensation, reasoning that this is the amount that a willing seller would accept in a voluntary sales transaction, and therefore it should also be payable in an involuntary one. However, the U.S. Supreme Court has repeatedly acknowledged that "fair market value" as defined by it falls short of what sellers would demand and receive in voluntary transactions.