Issue Preclusion

Issue preclusion, historically called collateral estoppel, prevents a party from re-arguing an issue that a court has already decided against it, even if the later lawsuit involves a different claim or cause of action. It is distinct from claim preclusion (res judicata in the narrow sense), which bars relitigation of the entire claim, not just discrete issues.

In U.S. federal practice, courts generally apply four requirements drawn from the Restatement (Second) of Judgments §27: (1) the issue in the second action is identical to one decided in the first; (2) the issue was actually litigated; (3) its determination was necessary to the prior judgment; and (4) the party against whom preclusion is asserted had a full and fair opportunity to litigate it.

The U.S. Supreme Court expanded the doctrine in two important ways. In Blonder-Tongue Laboratories v. University of Illinois Foundation, 402 U.S. 313 (1971), it permitted defensive non-mutual issue preclusion, allowing a new defendant to invoke a prior loss by the plaintiff. In Parklane Hosiery Co. v. Shore, 439 U.S. 322 (1979), the Court approved offensive non-mutual issue preclusion, subject to trial-court discretion to prevent unfairness.

In English law, the analogous doctrine is issue estoppel, recognized in cases such as Arnold v National Westminster Bank plc [1991] 2 AC 93, with somewhat narrower scope than its U.S. counterpart.

For international researchers, the principle surfaces in investor-state arbitration and before bodies like the International Court of Justice, though the ICJ tends to speak of res judicata generally (see Application of the Genocide Convention (Bosnia v. Serbia), Judgment of 26 February 2007, paras. 114–141) rather than parsing issue versus claim preclusion as sharply as common-law courts do.

Limits include changes in controlling law, new evidence unavailable earlier, and issues resolved only as alternative or non-essential grounds.