Summary. Preclusion doctrine decides which fights are over, through two mechanisms practitioners routinely blend together. Claim preclusion bars an entire second lawsuit on the same transaction, including theories never raised; issue preclusion bars relitigation of a specific issue actually litigated and necessarily decided. This article separates them, works each element in the order a court considers it, and covers the counterintuitive areas: nonparty preclusion after Taylor v. Sturgell, the abandonment of mutuality and the discretion courts retain over offensive use, what preclusive effect a federal court gives a state judgment and vice versa, and when an agency or arbitrator can decide something that binds a court. It closes with the pleading and waiver rules that decide these questions in practice.

A distributor sues a manufacturer for breach of a supply agreement and loses on summary judgment because the agreement was terminable at will. Two years later the distributor sues again — same agreement, same termination, same facts — this time for fraudulent inducement and tortious interference.

That second case is barred, and not because a court decided the fraud claim. Nobody decided it. It is barred because claim preclusion extends to every theory arising from the same transaction that could have been raised, whether or not it was.

Now change one fact. The second suit is against a different defendant — the manufacturer's parent company, which was not a party the first time. Suddenly the analysis changes completely: claim preclusion probably does not apply, but the parent may be able to use issue preclusion to establish that the agreement was terminable at will, even though the parent would not have been bound by a contrary ruling.

Those two doctrines are related in name and almost nothing else, and the single most useful discipline in this area is refusing to say "res judicata" when you mean one specific thing.

Vocabulary

  • Res judicata, in its narrow modern usage, means claim preclusion. In older cases and in many state opinions it is used broadly to cover both doctrines. Read carefully.
  • Claim preclusion bars a second action on the same claim between the same parties or their privies after a final judgment on the merits.
  • Collateral estoppel, or issue preclusion, bars relitigation of a specific issue that was actually litigated and necessarily decided in a prior action.
  • Merger describes what happens to a plaintiff's claim when it wins: the claim merges into the judgment. Bar describes what happens when the plaintiff loses.
  • The Restatement (Second) of Judgments is the standard reference and is followed, in substance, by the federal courts and most states.

Claim preclusion

Three elements, each of which is fought over.

1. A final judgment on the merits

Final in the trial court. Most jurisdictions give a judgment preclusive effect even while an appeal is pending, though a reversal wipes it out — which is why the practical answer is often to seek a stay of the second action rather than a ruling.

On the merits is a term of art that has drifted from its literal meaning. Judgments that count:

  • Judgment after trial or on a jury verdict.
  • Summary judgment.
  • Default judgment — preclusive as to the claim in most jurisdictions, though not as to issues, because nothing was actually litigated.
  • Dismissal for failure to state a claim. Federated Department Stores, Inc. v. Moitie, 452 U.S. 394 (1981), confirms that a Rule 12(b)(6) dismissal is on the merits and precludes a later action, even where the governing law later changes.
  • Consent judgment and settlement, to the extent the parties intended. The scope of the release, not preclusion doctrine, usually does the work; draft it that way.
  • Dismissal with prejudice for failure to prosecute or to comply with an order, under Rule 41(b).

Judgments that are not on the merits: dismissal for lack of subject-matter jurisdiction, personal jurisdiction, improper venue, or failure to join a party under Rule 19 — Rule 41(b) expressly excepts these. They preclude relitigation of the jurisdictional determination itself, but not of the underlying claim.

A trap worth knowing. Semtek International Inc. v. Lockheed Martin Corp., 531 U.S. 497 (2001), held that Rule 41(b)'s "adjudication on the merits" language means only that the plaintiff cannot refile in the same court — it does not itself determine preclusive effect elsewhere. The preclusive effect of a federal diversity judgment is governed by federal common law, which adopts the law of the state in which the federal court sits unless that law is incompatible with federal interests. So a California federal court's statute-of-limitations dismissal precludes a Maryland action only if California law would give it that effect. Practitioners assume a nationally uniform federal rule here and are frequently wrong.

2. Same parties or privies

The judgment binds the parties and those in privity with them. Traditional privity categories:

  • Successors in interest to property that was the subject of the action.
  • Persons who controlled the prior litigation — an indemnitor funding and directing the defense, an insurer, a parent directing a subsidiary's case.
  • Persons represented by a party in a representative capacity — class members, beneficiaries of a trust, estates.
  • Agents and principals, in the specific circumstances where a judgment for the agent precludes a vicarious liability claim against the principal.

The Supreme Court cleaned this up. Taylor v. Sturgell, 553 U.S. 880 (2008), rejected the "virtual representation" doctrine that several circuits had developed, holding that nonparty preclusion is limited to six categories:

  1. The nonparty agreed to be bound.
  2. A substantive legal relationship exists — preceding and succeeding owners of property, bailee and bailor, assignor and assignee.
  3. The nonparty was adequately represented by someone with the same interests — class actions, suits by trustees, guardians, and other fiduciaries.
  4. The nonparty assumed control over the prior litigation.
  5. The nonparty is litigating as a proxy or designated representative of a party bound by the judgment.
  6. A special statutory scheme forecloses successive litigation — bankruptcy, probate, quiet title, and certain in rem proceedings.

Taylor is the citation to reach for whenever an opponent argues that a non-party should be bound because it was "closely aligned" with a losing litigant. The Court grounded the limits in due process: a person who was not a party generally cannot be bound by a judgment, and the exceptions are narrow.

3. Same claim

This is the element courts actually decide, and the test varies.

The transactional test — Restatement (Second) § 24, followed in the federal courts and most states. A claim includes all rights of the plaintiff to remedies against the defendant with respect to all or any part of the transaction, or series of connected transactions, out of which the action arose. What constitutes a "transaction" is determined pragmatically: whether the facts are related in time, space, origin, or motivation, whether they form a convenient trial unit, and whether treating them as a unit conforms to the parties' expectations or business understanding.

The consequence practitioners must internalize: claim preclusion bars theories never pleaded. The distributor in the opening example lost the fraud claim it never brought. This is why complaints should plead alternative theories arising from the same facts even when some seem weak — the alternative is losing them permanently.

Older and narrower tests survive in some states: the "same evidence" test, the "primary rights" theory (California, where a single act invading two primary rights supports two claims), and the "same cause of action" formulations. In a multi-jurisdictional dispute, identify the test of the rendering forum before predicting anything.

Exceptions to the same-claim bar, from Restatement § 26:

  • The parties agreed the plaintiff could split the claim, or the defendant acquiesced.
  • The court in the first action expressly reserved the plaintiff's right to maintain the second.
  • The plaintiff was unable to seek a remedy in the first action because of jurisdictional limitations — a claim within exclusive federal jurisdiction that could not have been brought in the state action.
  • The judgment was plainly inconsistent with a fair and equitable implementation of a statutory scheme.
  • Continuing or recurring conduct giving rise to new claims after the first judgment. A trademark owner who lost an infringement suit may sue over later infringements; the events are different transactions.

Compulsory counterclaims. Rule 13(a) requires a pleading to state a counterclaim arising out of the same transaction or occurrence as the opposing party's claim. A defendant who does not assert it loses it — functionally a claim-preclusion rule operating against defendants. State practice varies, and a few states have permissive counterclaim regimes.

Defenses are different. Lucky Brand Dungarees, Inc. v. Marcel Fashions Group, Inc., 590 U.S. 405 (2020), held unanimously that there is no freestanding "defense preclusion" outside the ordinary rules. Because the second suit involved different conduct and different marks occurring after the first judgment, the claims were not the same, and a defense that could have been raised earlier was not barred. The lesson: run the same-claim analysis before assuming an unraised defense is lost.

Issue preclusion

Four elements, and a fifth consideration that is really a discretion check.

1. The same issue

Identity of issue is stricter than identity of claim. The issue must be identical in law and fact, not merely similar. Changes in the governing legal standard, in the burden of proof, or in the factual context defeat identity.

Burden of proof matters enormously. A defendant acquitted in a criminal case is not entitled to preclusion in a subsequent civil action, because the government bore a higher burden. Conversely, a criminal conviction generally does preclude relitigation of the elements in a later civil case, because the higher burden was met.

2. Actually litigated

The issue must have been raised, contested, and submitted for determination. This excludes:

  • Default judgments. Nothing was litigated.
  • Consent judgments and settlements, absent express agreement that specified issues are determined.
  • Admissions and stipulations, which resolve issues without litigating them — though a stipulation may be binding as a matter of contract in the same case.
  • Issues resolved by a failure to respond.

3. Necessarily decided

The determination must have been essential to the judgment. Alternative holdings create a well-known split: the Restatement (Second) takes the position that where a judgment rests on two independent alternative grounds, neither is conclusive, because neither was necessary and neither may have been carefully considered or appealed. Some courts, and the first Restatement, treat both as preclusive. Federal courts have gone both ways.

Dicta is never preclusive, and the exercise of distinguishing an essential finding from an observation is the core of most issue-preclusion briefing. Read the prior opinion for what the judgment required, not for everything the court said.

4. A full and fair opportunity to litigate

The party to be bound must have had one. Courts examine incentive to litigate (was the first case small stakes?), procedural differences (were discovery or appellate rights limited?), foreseeability of future litigation, and whether the party could have obtained review.

Mutuality, and its demise

The traditional rule required mutuality: a party could invoke a judgment only if it would also have been bound by it. That rule is gone in federal practice and in most states, but the two directions are treated very differently.

Defensive nonmutual issue preclusion — a defendant who was not a party to the first case uses a prior judgment to prevent a plaintiff from relitigating an issue the plaintiff lost. Blonder-Tongue Laboratories, Inc. v. University of Illinois Foundation, 402 U.S. 313 (1971), approved it in the patent context: a patentee whose patent was held invalid in a suit against one infringer cannot relitigate validity against another. Defensive use is broadly permitted, because it encourages a plaintiff to join all defendants in one action.

Offensive nonmutual issue preclusion — a plaintiff who was not a party to the first case uses a judgment against a defendant that lost the issue there. Parklane Hosiery Co. v. Shore, 439 U.S. 322 (1979), permitted it but committed it to the trial court's discretion, identifying factors that counsel against:

  • The plaintiff could easily have joined the earlier action — the "wait and see" plaintiff who lets someone else test the case.
  • The defendant had little incentive to litigate vigorously in the first action, because the stakes were small or the forum inconvenient.
  • The judgment relied on is inconsistent with other judgments in the defendant's favor.
  • The second action affords procedural opportunities unavailable in the first that could produce a different result.

And note the federal-government exception. United States v. Mendoza, 464 U.S. 154 (1984), held that nonmutual offensive collateral estoppel does not apply against the United States, so the government may relitigate the same legal issue in different circuits — which is how circuit splits develop on questions the government has already lost.

Judgments from other systems

State judgments in federal court

28 U.S.C. § 1738, the full faith and credit statute, directs federal courts to give state judgments the same preclusive effect they would have in the rendering state's own courts. Not more, not less. That means the rendering state's preclusion law governs, including its test for identity of claims.

Allen v. McCurry, 449 U.S. 90 (1980), applied § 1738 to bar a § 1983 action relitigating a Fourth Amendment issue decided in a state criminal suppression hearing, rejecting the argument that § 1983 plaintiffs are entitled to a federal forum. Marrese v. American Academy of Orthopaedic Surgeons, 470 U.S. 373 (1985), refined the analysis for claims within exclusive federal jurisdiction: first ask what preclusive effect the state would give its own judgment; only if the state would preclude does the court ask whether an exception to § 1738 should apply because the federal statute impliedly repealed it.

Federal judgments in state court

Federal common law governs, and for federal-question judgments applies a uniform federal rule. For diversity judgments, Semtek directs incorporation of the forum state's law, as described above.

Foreign country judgments

Not covered by § 1738. Recognition proceeds under state law, usually the Uniform Foreign-Country Money Judgments Recognition Act, which requires a final, conclusive, and enforceable money judgment and permits non-recognition where the rendering system lacked impartial tribunals or due process, where personal or subject-matter jurisdiction was lacking, or on discretionary grounds including fraud, public policy, and inconsistency with another judgment.

Administrative agency determinations

Agency findings can preclude, but the test is functional. University of Tennessee v. Elliott, 478 U.S. 788 (1986), held that when a state agency acting in a judicial capacity resolves disputed issues of fact properly before it and the parties had an adequate opportunity to litigate, federal courts give the findings preclusive effect as a matter of federal common law — though the Court held such findings do not preclude a Title VII claim, given that statute's structure. Astoria Federal Savings & Loan Ass'n v. Solimino, 501 U.S. 104 (1991), similarly found the ADEA's structure incompatible with preclusion from state agency findings.

The most consequential modern application is B&B Hardware, Inc. v. Hargis Industries, Inc., 575 U.S. 138 (2015). The Court held that a Trademark Trial and Appeal Board decision on likelihood of confusion can preclude relitigation in a district court infringement action, where the ordinary elements of issue preclusion are met and the usages adjudicated by the Board are materially the same as those before the court. The practical effect was significant: an opposition or cancellation proceeding, once treated as a low-stakes registration dispute, became something that can decide an infringement case. Litigants now think hard about whether to fight in the TTAB at all, and about whether to seek suspension of a Board proceeding pending district court litigation.

Arbitration awards

A confirmed award is generally given preclusive effect between the parties. Whether an award precludes issues in litigation with nonparties is more contested, and courts weigh the informality of the proceeding, the absence of full discovery and reasoned findings, and the parties' expectations. Where an award contains no findings — common in commercial arbitration — issue preclusion has nothing to attach to, which is a reason to request a reasoned award if preclusion is desired.

Bankruptcy

Confirmation of a plan is res judicata as to issues that could have been raised, and courts enforce that vigorously against creditors who slept on objections. Dischargeability determinations preclude relitigation. And a proof of claim allowed or disallowed is a final judgment for preclusion purposes.

Neighboring doctrines that are not preclusion

Law of the case. A court's decision on a legal issue governs later stages of the same case. It is a discretionary policy rather than a jurisdictional limit — a court may revisit its own interlocutory rulings, though the mandate rule binds a lower court on remand as to issues decided by the appellate court, expressly or by necessary implication.

Judicial estoppel. Prevents a party from asserting a position clearly inconsistent with one successfully maintained earlier. New Hampshire v. Maine, 532 U.S. 742 (2001), identified the non-exhaustive factors: whether the position is clearly inconsistent, whether the party succeeded in persuading a court to accept the earlier position, and whether the party would derive an unfair advantage if not estopped. It protects the integrity of the judicial process rather than the opposing party, so reliance is not required.

The most common commercial application: a debtor who fails to schedule a lawsuit as an asset in bankruptcy and then prosecutes it. Courts frequently estop the claim, though many now examine whether the omission was inadvertent and whether the trustee has been substituted, since dismissing the claim punishes creditors rather than the debtor.

Election of remedies, waiver, and release. Contract and equity doctrines, not preclusion, though they occupy similar ground and are often pleaded together.

Stare decisis. Precedential effect of legal rulings on other parties, which is a rule about law rather than about a particular judgment's binding effect.

Procedure: raising it, waiving it, and proving it

It is an affirmative defense. Rule 8(c) lists both res judicata and estoppel among the defenses that must be affirmatively pleaded. Failure to plead generally waives it, subject to the usual practice of permitting amendment where the opponent is not prejudiced. Some courts permit a court to raise preclusion sua sponte where the prior judgment was rendered by the same court, or in the interest of avoiding duplicative litigation, but this cannot be counted on.

How to raise it:

  • Motion to dismiss where the prior judgment appears on the face of the complaint or is subject to judicial notice. Courts routinely take judicial notice of court records for the fact of a judgment and its contents, though not for the truth of disputed factual findings.
  • Motion for judgment on the pleadings after answering.
  • Summary judgment, which is the cleanest vehicle because it permits a full record of the prior proceedings.

Proving it. Assemble and authenticate:

  • The prior complaint, to establish the transaction and the claims asserted.
  • The judgment and any opinion or order, to establish what was decided.
  • For issue preclusion, whatever shows the issue was actually litigated and necessarily decided: the summary judgment briefing, the jury instructions and verdict form, findings of fact, or the trial transcript.
  • The docket, to establish finality and the absence or resolution of an appeal.

Jury verdicts are hard to parse. A general verdict for the defendant does not establish which element failed, and issue preclusion generally will not attach. This is a reason to request special interrogatories or a special verdict form in a case likely to spawn follow-on litigation, and a reason to resist them if you expect to be the one relitigating.

Anticipating preclusion when drafting. In a settlement, say explicitly whether the resolution is intended to have preclusive effect, and as to which issues. In a consent judgment, recite findings if you want them to bind, and disclaim them if you do not. In a dismissal, specify with or without prejudice, and consider whether Rule 41(a)(1)(B)'s two-dismissal rule is in play.

A working checklist

When a client says "we already litigated this," work through the following in order.

  1. Identify the prior proceeding precisely — court, parties, claims, disposition, date, appeal status.
  2. Determine which preclusion law governs. Rendering court's, under § 1738 for state judgments and under Semtek for federal diversity judgments.
  3. Was there a final judgment on the merits? Check the basis for dismissal against the Rule 41(b) exceptions.
  4. Same parties or privies? Run the six Taylor categories rather than reaching for a general alignment-of-interests argument.
  5. Same claim, under the rendering forum's test? Apply the transactional test pragmatically; identify whether any Restatement § 26 exception applies.
  6. If claim preclusion fails, go issue by issue. For each issue: identical? actually litigated? necessarily decided? full and fair opportunity?
  7. If invoking issue preclusion nonmutually, and offensively, address the Parklane factors affirmatively in your brief. Courts deny offensive use routinely, and the party invoking it should explain why joinder was impractical and why the defendant had every incentive to litigate.
  8. Check for the neighboring doctrines — judicial estoppel, law of the case, release — which sometimes reach conduct preclusion misses.
  9. Plead it in the answer, without exception.

Why the doctrine looks harsh and mostly is not

Claim preclusion regularly extinguishes claims that no one evaluated. That is the point people find hardest to accept, and it is worth stating the justification plainly: a system that lets a losing party return with a new theory each time imposes the cost of endless litigation on the winner, on later litigants waiting for a courtroom, and on the reliability of judgments generally. The rule that you must bring everything arising from a transaction at once is the price of a judgment meaning something.

The corresponding obligation falls on the plaintiff's lawyer at the outset. Plead the whole transaction. Identify every theory the facts support and every defendant who might be liable, and if you choose to leave something out — for strategy, for jurisdiction, for cost — understand that you are choosing to lose it, and write down why. The distributor in the opening example probably had counsel who thought the fraud claim was weak. It may have been. It was also worth exactly nothing after the summary judgment order, and nobody ever found out.

Parallel proceedings: managing preclusion in real time

Most preclusion problems are created while two cases are running simultaneously, and the party that thinks about the second case while litigating the first has enormous advantages.

The race to judgment. When the same dispute is pending in two forums, the first judgment entered controls, regardless of which case was filed first. That single rule drives a great deal of tactical behavior: a defendant facing a strong claim in state court may push a related declaratory action in federal court toward summary judgment; a plaintiff who filed second may seek an expedited trial setting. Courts have tools to manage this — the first-to-file rule among federal courts, Colorado River abstention, anti-suit injunctions in the international context, and ordinary stays — but none of them is automatic, and a party that assumes the court will sort it out often finds that it did not.

Consolidation and coordination. Where both actions are in the same system, move to consolidate under Rule 42 or to transfer under 28 U.S.C. § 1404. Multi-district litigation under § 1407 coordinates pretrial proceedings but does not merge the cases for preclusion purposes, and a bellwether verdict does not bind absent plaintiffs — a point that gets confused in settlement negotiations.

Bifurcation creates preclusion exposure. A court that tries liability first and damages later has created a judgment on liability that may bind in other cases before the defendant has had any opportunity to appeal. Where follow-on litigation is likely, consider whether to seek entry of judgment under Rule 54(b) so that appellate review is available, or to resist bifurcation for that reason.

Preserving issues for the second case. If a party expects related litigation, it should build the record to control what is "necessarily decided." That means special verdict forms where narrow findings help and general verdicts where they do not; explicit reservations on the record when a court declines to reach an issue; and, where a court's opinion contains language that could be read as a broader holding than the judgment required, a motion to clarify or amend under Rule 59(e) before the window closes.

Settlements in serial litigation. A defendant settling the first of many similar cases should insist that the settlement be documented as a compromise with no findings, no admissions, and an express statement that nothing is intended to have preclusive or evidentiary effect in any other proceeding. A plaintiff in the same posture wants the opposite where it can get it — but a defendant will rarely agree, and the more realistic plaintiff-side goal is a factual stipulation limited to the settling case that nonetheless survives as an admission.

Appeal, or accept the finding. Because an unappealed adverse finding can bind in later cases, the decision whether to appeal a judgment is not only about the money at stake in that case. A defendant that accepts a modest judgment rather than appealing a damaging liability finding may be buying a preclusion problem worth many multiples of the judgment. Conversely, a party that appeals and loses converts a trial-court finding into circuit precedent, which is worse. That calculation belongs in the post-trial memo, and it is regularly omitted.

Three worked problems

Problem one. A franchisee sues a franchisor in state court for breach of the franchise agreement and loses after a bench trial. It then files in federal court asserting a Lanham Act false advertising claim and a federal antitrust tying claim, both arising from the same course of dealing. Analysis: the state judgment gets the preclusive effect state law would give it, under § 1738. The Lanham Act claim could have been brought in state court — federal jurisdiction over Lanham Act claims is not exclusive — so if the state uses a transactional test, it is barred. The antitrust claim is within exclusive federal jurisdiction, so Marrese applies: ask first whether the state would preclude a claim its courts could not have heard. Most states would not, and the antitrust claim likely survives claim preclusion — but the findings from the bench trial about what the parties agreed to may bind under issue preclusion.

Problem two. An employer wins an arbitration against one former employee on the enforceability of a non-compete, obtaining a reasoned award construing the covenant. It then sues a second former employee. Analysis: claim preclusion does not apply — different party, different claim. Offensive nonmutual issue preclusion is not available to the employer either, because the second employee was not a party to the arbitration and cannot be bound consistent with due process under Taylor. Conversely, if the employer had lost the first arbitration, the second employee might well be able to use the award defensively under Blonder-Tongue — subject to arguments about the adequacy of arbitral procedures. The asymmetry is the point: preclusion runs against parties, not for them.

Problem three. A company opposes a trademark application before the TTAB and loses on likelihood of confusion. The applicant then sues for a declaratory judgment of non-infringement. Analysis: under B&B Hardware, the Board's determination may preclude relitigation if the usages adjudicated by the Board are materially the same as the marketplace usages at issue in court. The fight will be over that comparison — the Board evaluates the mark as described in the application, which often differs from real-world use in trade dress, channels, and consumer sophistication. A party that wants to avoid preclusion should build a record of those differences during the Board proceeding, not after.

Each of these turns on a distinction that is easy to state and easy to miss under time pressure: who was a party, what tribunal had authority over what, and whether the second dispute is the same transaction or merely a similar one. Answer those three questions before writing a word of the brief.

Related articles

This article is provided for general informational purposes and does not constitute legal advice. Preclusion law varies by jurisdiction, particularly on the test for claim identity and on the effect of alternative holdings, and the governing law is that of the rendering forum. Consult qualified litigation counsel before relying on or resisting a prior judgment.