Also known as: unwritten laws · common law · customary law · lex non scripta
Written by attorneys · grounded in primary & secondary sources — see below
Law sanctioned by custom rather than by enactment in statutes or ordinances. It includes case law derived from judicial decisions that courts ascertain through reason and precedent.
Ulrike Ulrich drove recklessly through a residential neighborhood and struck a pedestrian who later died. Prosecutors charged her with involuntary manslaughter. The court applied the unwritten law to determine that an unlawful act causing death supports liability even without intent to kill.
Ugo Ucelli sued a neighbor for property damage exceeding twenty dollars. The defendant demanded a bench trial. The court recognized that the unwritten law preserved the right to a jury in such suits and ordered a jury trial.
Uliana Ustinova brought a contract claim in federal court based on diversity jurisdiction. The judge refused to create a new federal rule and instead followed the unwritten law of the forum state to decide the dispute.
Select any source to read its text and confirm it supports the definition.
Umar Usmani petitioned to adopt a child but discovered no common law procedure existed. The court directed him to comply with the state's adoption statute because the unwritten law had never recognized adoption.
Ursula Ureña refused to disclose therapy records in a civil case governed by state law. The court looked to the unwritten law as interpreted by reason and experience to uphold the psychotherapist privilege.
Una Ueda operated a delivery service and struck a pedestrian while backing up without checking mirrors. The court considered the unwritten law and general customs regarding safe driving practices when assessing whether her conduct created an unreasonable risk.
Unwritten law derives from custom and judicial decisions rather than legislative enactment. Courts ascertain its rules through precedent and reason instead of consulting codified text.
Supporting sources
Yes. The amendment preserves the right to jury trial in suits at common law where the amount in controversy exceeds twenty dollars and limits reexamination of jury facts except according to common law rules.
Federal courts must apply the substantive law of the state in which they sit, including its common law rules, rather than creating federal general common law to govern state claims.
No. Adoption was not recognized at common law and remains purely statutory. Courts require compliance with state adoption statutes to establish a valid adoption.
Federal Rule of Evidence 501 provides that the common law as interpreted by United States courts in light of reason and experience governs claims of privilege unless the Constitution, a federal statute, or Supreme Court rule provides otherwise.
Courts consider the common law, legislative enactments, and general customs when deciding whether an actor should recognize that conduct involves a risk to others.
…weights of the respective interests involved, with the lessons and examples of medical and legal history, with the lenity of the common law, and with the demands of the profound problems of the present day. The decision leaves the State free to place increasing restrictions on abortion as the period of pregnancy lengthens, so…