A court of the United States may not grant an injunction to stay proceedings in a State court except as expressly authorized by Act of Congress, or where necessary in aid of its jurisdiction, or to protect or effectuate its judgments.
28 U.S.C. § 2283
HISTORICAL AND REVISION NOTES Based on title 28, U.S.C., 1940 ed., §379 (Mar. 3, 1911, ch. 231, §265, 36 Stat. 1162).An exception as to acts of Congress relating to bankruptcy was omitted and the general exception substituted to cover all exceptions.The phrase "in aid of its jurisdiction" was added to conform to section 1651 of this title and to make clear the recognized power of the Federal courts to stay proceedings in State cases removed to the district courts.The exceptions specifically include the words "to protect or "effectuate its judgments," for lack of which the Supreme Court held that the Federal courts are without power to enjoin relitigation of cases and controversies fully adjudicated by such courts. (See Toucey v. New York Life Insurance Co., 62 S.Ct. 139, 314 U.S. 118, 86 L.Ed. 100. A vigorous dissenting opinion (62 S.Ct. 148) notes that at the time of the 1911 revision of the Judicial Code, the power of the courts, of the United States to protect their judgments was unquestioned and that the revisers of that code noted no change and Congress intended no change). Therefore the revised section restores the basic law as generally understood and interpreted prior to the Toucey decision.Changes were made in phraseology.