Petitioner manufacturers and distributes bakery products in California. A union sought unsuccessfully to organize its employees. Thereupon, the union sought to enlist the aid of purchasers and consumers of petitioner's products. Agents of the union requested retail stores not to handle petitioner's products and stated that if they continued to do so, a picket line would be set up. Some stores acquiesced; others did not. The union placed pickets at the entrances of the latter stores, with the result that many deliveries were interrupted and some employees of other employers refused to cross the picket lines.

Petitioner made two counter moves. First, it filed suit for an injunction against the union in the California courts. A few days later it filed a charge of an unfair labor practice against the union with respondent. Each had as a basis the same conduct of the union.

On April 7, 1952, the California court issued a preliminary injunction against the union, banning all picketing of retail stores. On May 14, 1952, the Regional Director of respondent concluded, after investigation, that insofar as the conduct of the union involved merely an appeal to customers and to the public in general, it was lawful under the National Labor Relations Act, as amended, 49 Stat. 449, 61 Stat. 136, 29 U.S.C. § 151 et seq., 29 U.S.C.A. § 151 et seq.; but that it was unlawful, insofar as it induced or encouraged employees of employers other than petitioner to refuse to perform services at the picketed places. The Regional Director, acting on behalf of the General Counsel, issued an unfair labor practice complaint against the union on that limited basis. On the same day, he petitioned the Federal District Court for an injunction restraining such conduct of the union, pending final adjudication by the Board, as required by § 10(l) of the Act.1

Simultaneously with the filing of the § 10(l) petition against the union, the Board filed suit in the same District Court, asking that petitioner be enjoined from enforcing the state court injunction. The District Court concluded that the conduct of the union, in the respects stated, was subject to the exclusive jurisdiction of the Board and that the action of the state court invaded the exclusive jurisdiction of the Board and the District Court. It accordingly granted the relief prayed for. The Court of Appeals affirmed. 204 F.2d 848. The case is here on a petition for a writ of certiorari limited to the following question:

"In view of the fact that exclusive jurisdiction over the subject matter was in the National Labor Relations Board, Garner v. Teamsters, Chauffeurs and Helpers Local Union No. 776 (A.F.L.) (346 U.S. 485), 74 S.Ct. 161, could the Federal District Court, on application of the Board, enjoin Petitioners from enforcing an injunction already obtained from the State court?" 346 U.S. 936, 74 S.Ct. 375.

I. The District Court had jurisdiction of the subject matter, because this is a 'civil action or proceeding' arising under an Act of Congress 'regulating commerce.' 28 U.S.C. § 1337, 28 U.S.C.A. § 1337. The National Labor Relations Act is a law 'regulating commerce' (National Labor Relations Board v. Jones & Laughlin Steel Corp., 301 U.S. 1, 57 S.Ct. 615, 81 L.Ed. 893); and here, as in American Federation of Labor v. Watson, 327 U.S. 582, 591, 66 S.Ct. 761, 765, 90 L.Ed. 873, the rights asserted arise under that law.

II. In absence of a command of the Congress to the contrary, the power of the District Court to issue the injunction is clear. Federal courts seek to avoid needless conflict with state agencies and withhold relief by way of injunction where state remedies are available and adequate. See Alabama Public Service Commission v. Southern Ry. Co., 341 U.S. 341, 71 S.Ct. 762, 95 L.Ed. 1002. But where Congress, acting within its constitutional authority, has vested a federal agency with exclusive jurisdiction over a subject matter and the intrusion of a state would result in conflict of functions, the federal court may enjoin the state proceeding in order to preserve the federal right. See Public Utilities Commission of Ohio v. United Fuel Gas Co., 317 U.S. 456, 468—470, 63 S.Ct. 369, 375—376, 87 L.Ed. 396; Bowles v. Willingham, 321 U.S. 503, 510—511, 64 S.Ct. 641, 645, 88 L.Ed. 892. Cf. American Federation of Labor v. Watson, supra, 327 U.S. at pages 593—595, 66 S.Ct. at pages 766—767, 90 L.Ed. 873. Congress, however, has provided that '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, 28 U.S.C.A. § 2283.

We do not stop to consider the many questions which have been propounded under this newly worded provision of the Code.2 One alone suffices for this case. For we conclude that the injunction issued by the District Court was 'necessary in aid of its jurisdiction' and thus permitted under the exceptions specifically allowed by Congress.

The state court injunction restrains conduct which the District Court was asked to enjoin in the § 10(l) proceeding brought in the District Court by the Board's Regional Director against the union. In order to make the § 10(l) power effective the Board must have authority to take all steps necessary to preserve its case. If the state court decree were to stand, the Federal District Court would be limited in the action it might take. If the Federal District Court were to have unfettered power to decide for or against the union, and to write such decree as it deemed necessary in order to effectuate the policies of the Act, it must be freed of all restraints from the other tribunal. To exercise its jurisdiction freely and fully it must first remove the state decree. When it did so, it acted 'where necessary in aid of its jurisdiction'.

Affirmed.

Mr. Justice BLACK dissents.

Mr. Justice JACKSON took no part in the consideration or decision of this case.