Smith v. Bayer Corp.

Holding: A federal district court exceeded its authority under the core litigation exception of the Anti-Injunction Act when it enjoined a state court from considering a request for class certification; the district court's denial of a similar class-certification request by a different plaintiff did not preclude other plaintiffs from proceeding in state court when it is unclear whether the certification issues in the same court were the same and the state plaintiffs were neither a party to the federal suit nor covered by any exceptions to the rule against nonparty preclusion.

Judgment: Eighth Circuit reversed, 9-0, in an opinion by Justice Elena Kagan on June 16, 2011. Justice Thomas joins only Parts I and II-A of the Court’s opinion.