Ghassan Korban, in His Official Capacity as Executive Director of the Sewerage and Water Board of New Orleans v. Watson Memorial Spiritual Temple of Christ, dba Watson Memorial Teaching Ministries, et al.

“[C]laim preclusion prevents parties from raising issues that could have been raised and decided in a prior action—even if they were not actually litigated.” Lucky Brand Dungarees, Inc. v. Marcel Fashions Grp., Inc., 590 U.S. 405, 412 (2020). “The preclusive effect of the judgment of a federal court is governed by federal law, regardless of whether that judgment’s preclusive effect is later asserted in a state or federal forum.” Herrera v. Wyoming, 587 U.S. 329, 360 n.4 (2019) (Alito, J., dissenting) (citing Taylor v. Sturgell, 553 U.S. 880, 892 (2008)). Some state courts, however, such as the Supreme Court of Louisiana, have manufactured an exception to this rule based on their speculation about whether the federal court in the prior action would have declined discretionary jurisdiction over pendent statelaw claims had the relevant claims actually been raised. Other courts refuse to engage in such “an exercise of prognosticative futility,” and instead require plaintiffs to raise all potential state-law claims in the federal action. Anderson v. Phoenix Inv. Couns. of Bos., Inc., 387 Mass. 444, 451, 440 N.E.2d 1164, 1168 (1982). Given this split, the question presented is: Is a prior federal judgment res judicata as to state-law claims in a subsequent state- or federalcourt action that arise from a common core of facts and that could have been, but were not, raised in the prior federal action?