In a case where a Federal District Court enjoined a state court from considering a plaintiff's request to approve a class action, the Eight Circuit Court of Appeals affirmation of the District Court's grant of injunction is reversed, because in enjoining a state court from considering petitioner's class certification request, the federal court exceeded its authority under the "relitigation exception" to the Anti-Injunction Act, 28 U.S.C. section 2283.