Neptunian Preclusion

In the course of resolving a long-running dispute about arbitration, the Fifth Circuit highlighted an important but infrequently litigated collateral-estoppel issue:

…  an unappealable ruling like a remand order is not entitled to preclusive effect. Beiser v. Weyler, 284 F.3d 665, 673 (5th Cir. 2002) (explaining that when “a litigant, as a matter of law, has no right to appellate review, then he has not had a full and fair opportunity to litigate and the issue is not precluded”); see Winters v. Diamond Shamrock Chem. Co., 149 F.3d 387, 395 (5th Cir. 1998) (suggesting that “collateral estoppel may not be applied offensively to a jurisdictional decision—such as one granting a motion to remand—that is not capable of being subjected to appellate review”) …  The unappealability of remand orders is why, after a remand, a state court may revisit the federal court’s jurisdictional reasoning. … We recognized this principle in dismissing the appeal of the 2002 remand: “[T]he district court determined that the arbitration clause was invalid in the process of ascertaining whether it had subject matter jurisdiction,” which meant the ruling “has no preclusive effect in state court.” Dahiya, 371 F.3d at 211. The state court could freely reexamine the issue and “reach a different conclusion about [the] dispute’s arbitrability.” Beiser, 284 F.3d at 674.

Neptune Shipmanagement Services v. Dahiya, No. 20-30776 (Oct. 1, 2021) (emphasis added).