## Facts

- West Virginia consumers sued Bayer in West Virginia state court, seeking certification of a statewide class of purchasers of Baycol, a prescription drug later withdrawn from the market.
- In related federal multidistrict litigation in Minnesota, a different plaintiff sought certification of a similar West Virginia economic-loss class under Federal Rule of Civil Procedure 23.
- The federal MDL court denied class certification, finding individualized issues (including damages) predominated.
- Bayer then sought a federal injunction barring the West Virginia state court from considering the state plaintiffs’ class-certification motion under West Virginia Rule of Civil Procedure 23.
- The federal district court issued the injunction under the Anti-Injunction Act’s relitigation exception; the Eighth Circuit affirmed.

## Issues

1. Whether the Anti-Injunction Act’s relitigation exception authorized a federal court to enjoin a state court from considering class certification after a federal court denied certification in a similar case.
2. Whether the state class-certification question was “the same issue” as the one decided under Federal Rule 23, given possible differences in state-law interpretation of a parallel procedural rule.
3. Whether unnamed members of a proposed but uncertified federal class can be bound (for preclusion purposes) by the federal denial of class certification.

## Decision

- The Supreme Court unanimously reversed and held the federal court exceeded its authority in enjoining the state proceeding.
- The relitigation exception did not apply because the state and federal certification issues were not shown to be identical.
- The relitigation exception also did not apply because the state plaintiffs were not parties to, and were not bound by, the federal action in which certification had been denied.
- The injunction against the West Virginia proceedings was vacated.

## Legal Principles

- The Anti-Injunction Act, 28 U.S.C. § 2283, strongly disfavors federal injunctions against state-court proceedings; its exceptions are narrow and doubts are resolved in favor of allowing state courts to proceed.
- The relitigation exception permits an injunction only to prevent litigation of an issue previously presented to and decided by the federal court, consistent with ordinary claim and issue preclusion rules.
- Issue preclusion requires identity of issues; a state court may interpret a state procedural rule modeled on Federal Rule 23 differently, so parallel wording does not alone establish identity.
- As a general rule, only parties (or those in privity) are bound by a judgment; nonparty preclusion is limited.
- A denial of class certification does not create a certified class, and absent members of a proposed but uncertified class are not parties for purposes of being bound by the denial.

## Conclusion

The Court held that a prior federal denial of class certification did not justify enjoining a later state-court certification request by different plaintiffs because the state certification question was not necessarily identical and the state plaintiffs, as nonparties to an uncertified federal class, were not bound by the federal ruling.


Smith v. Bayer Corp., 564 U.S. 299 (2011)