In terrorem clauses routinely are included in wills and trusts to guard against attacks by disgruntled beneficiaries. Their enforceability, however, depends on the governing jurisdiction. Many states will not enforce such clauses if the beneficiary had "probable cause" or acted in good faith in initiating proceedings, (e.g. California, Connecticut, Iowa, Kansas, Minnesota, North Carolina, Oklahoma, Oregon, Pennsylvania, South Carolina and Wisconsin. Alaska will not enforce such clauses in wills if probable cause exists, but will enforce them in trusts even if probable cause exists), or if probable cause on grounds such as fraud, lack of capacity, mistake or validity exists (e.g. Mississippi, New Hampshire, Oregon and South Carolina.).

Other states, like California, enforce such clauses against only certain types of contests, and still other states, including Indiana and Florida, will not enforce such clauses at all. New York is among the minority of states (e.g. Georgia and Massachusetts), that enforce in terrorem clauses, regardless of probable cause, subject to the following caveats.