Semtek International Incorporated v. Lockheed Martin Corporation
The Court held that federal common law governs the preclusive effect of a judgment entered in a federal court sitting in diversity.
531 U.S. 497 · No. 99-1551 · 2000 term · Rehnquist Court
Decided Feb 27, 2001 · argued Dec 5, 2000
Judicial power · Judicial administration: collateral estoppel or res judicata
Majority opinion: Antonin Scalia
The voteMajority
9–09 in the majority, 0 in dissent
No dissent (9–0)
Reversed and remanded. Semtek International Incorporated won.
What this ruling means
Reversed and remanded: the Supreme Court overturned the decision of the Maryland appellate court and sent the case back to that court for further proceedings that follow the Supreme Court’s ruling.
Semtek International Incorporated was the petitioner, the side that asked the Supreme Court to review the case. “Won” means the Court gave that side the result it asked for.
From the Supreme Court Database. A justice who agreed with the result but not the reasoning counts in the majority.
Summary
The opening of the case’s Wikipedia article: what the case was about and what the Court held.
Semtek v. Lockheed Martin, 531 U.S. 497 (2001), is a United States Supreme Court case in which the Court held that federal common law governs the preclusive effect of a judgment entered in a federal court sitting in diversity.
Data notes
The text is Wikipedia’s (CC BY-SA 4.0), matched to the case by its citation, docket number or name and year, and is not checked against the opinion. The site keeps the article’s opening section, ending on its last full sentence. The one-sentence summary under the title is the Decisions list’s: Wikipedia’s own ruling sentence, or, tagged “AI-written”, one Claude wrote from this opening.
How the justices voted
Each justice who took part, placed by their Martin–Quinn ideology score for the 2000 term. Filled: the 9 in the majority. Hollow: the 0 in dissent. Colour is the party of the president who appointed them.
Majority(9)
Antonin ScaliaWrote the majority opinion
John StevensJoined the majority
Ruth GinsburgJoined the majority
Stephen BreyerJoined the majority
David SouterJoined the majority
Sandra O'ConnorJoined the majority
Anthony KennedyJoined the majority
William RehnquistJoined the majority
Clarence ThomasJoined the majority
Dissent(0)
- None.
Data notes
Each justice’s vote and what they wrote are from the justice-centered file of the Supreme Court Database. “Wrote a concurrence” means the justice sided with the majority and wrote separately; a justice who dissented in part is counted on the side they took overall. A justice who wrote nothing is listed as joining their side.
Positions are each justice’s Martin–Quinn score for the case’s term, the same scores as the Ideology page: negative is more liberal, positive more conservative. A score sums up a justice’s votes across the whole term, so it says where they usually sit, not why they voted as they did here. The median line is the Court’s median justice that term.
The parties
Who brought the case to the Court, who answered it, and how it got there.
- Petitioner
- Semtek International IncorporatedBusiness, corporation
- Respondent
- Lockheed Martin CorporationAirline
- Reached the Court by
- Certiorari (the Court chose to hear it)
Data notes
The names are the two sides of the case’s title. The description under each is the Supreme Court Database’s category for that party, in its own wording. The petitioner is the side that asked the Supreme Court to review the decision below. “Why it was taken” appears only when the majority opinion says lower courts disagreed or were unsure about the question; reasons that would fit any case (“to resolve the question presented”, “an important question”) are left out.
The law at issue
The law the Court was asked to apply, and the kind of power it used to decide.
- Provision
- Federal Rules of Civil Procedure, including Appellate Procedure, or relevant rules of a circuit court Judicial Code, and admiralty rules
- Kind of law
- Court Rules
- Decided by
- Statutory construction
Data notes
The Supreme Court Database codes the main constitutional provision, statute or court rule each case turned on, and the basis of the decision: judicial review of a federal or state law, interpreting a statute, supervising the lower courts, and so on. A case can rest on more than one. “Overruled” counts only where the majority opinion says so.
Timeline
What happened at the Court and how the case got there, newest first.
- Feb 27, 2001DecidedDecided · Decided 9–0: reversed and remanded. Semtek International Incorporated won.
- Dec 5, 2000ArguedArgued · Oral argument before the Court.
- Not datedTaken upTaken up · The Supreme Court agreed to hear the case (certiorari).
- Not datedCourt belowCourt below · Decided by the Maryland appellate court: affirmed.
- Not datedBeganBegan · The case began in the Maryland trial court.
Data notes
From the Supreme Court Database: the court the case began in, the court whose decision the Supreme Court reviewed and what that court did, how the case came to the Court, and the dates of argument and decision. The database does not date the steps in the lower courts. Court names are the database’s.
Other decisions on the same issue
12 other argued cases since 1946 on judicial administration: collateral estoppel or res judicata, newest first.
- Keathley v. Buddy Ayers Construction146 S. Ct. 1532Jun 11, 2026 · 146 S. Ct. 1532Judicial power9–0Unanimous band
- Taylor v. Sturgell553 U.S. 880Jun 12, 2008 · 553 U.S. 880Judicial power9–0Unanimous band
- United States v. Stauffer Chemical Co.464 U.S. 165Jan 10, 1984 · 464 U.S. 165Judicial power9–0Unanimous band
- United States v. Mendoza464 U.S. 154Jan 10, 1984 · 464 U.S. 154Judicial power9–0Unanimous band
- Federated Department Stores, Inc., et al. v. Moitie et al.452 U.S. 394Jun 15, 1981 · 452 U.S. 394Judicial power8–18–1 band
- Parklane Hosiery Co., Inc., et al. v. Shore439 U.S. 322Jan 9, 1979 · 439 U.S. 322Judicial power8–18–1 band
- Ford v. Ford371 U.S. 187Dec 10, 1962 · 371 U.S. 187Judicial power9–0Unanimous band
- Callanan Road Improvement Co. v. United States et al.345 U.S. 507May 4, 1953 · 345 U.S. 507Judicial power8–18–1 band
- United States v. International Building Co.345 U.S. 502May 4, 1953 · 345 U.S. 502Judicial power9–0Unanimous band
- United States v. Munsingwear, Inc.340 U.S. 36Nov 13, 1950 · 340 U.S. 36Judicial power8–18–1 band
- Commissioner of Internal Revenue v. Sunnen333 U.S. 591Apr 5, 1948 · 333 U.S. 591Judicial power9–0Unanimous band
- Angel v. Bullington330 U.S. 183Feb 17, 1947 · 330 U.S. 183Judicial power6–36–3 band
Data notes
Every other orally argued case with a clear vote, from the 1946 term on, that the Supreme Court Database files under the same issue as this one. The database gives each case one issue from a list of about 270 (abortion, search and seizure of vehicles, the death penalty, and so on), whatever law it turned on.
Official record
Read the full opinion on Justia, the argument audio on Oyez and Wikipedia. Case data from the Supreme Court Database, Version 2026 Release 01, through the 2025 term.