The constitutionality of the strike vote provision of the Michigan labor mediation law1 is before us in this case. Appellants struck against Chrysler Corporation in May, 1948, without conforming to the prescribed state procedure. The strike was called to enforce demands for higher wages, and it was conducted peacefully. To enjoin possible criminal prosecution,2 appellants instituted this suit in the state courts, contending that the statute violated the Due Process and Commerce Clauses of the Federal Constitution, Amend. 14; art. 1, § 8, cl. 3. The trial court upheld their contentions but the Michigan Supreme Court reversed. 1949, 325 Mich. 250, 38 N.W.2d 421. We find no need to discuss the due process point, inasmuch as we hold that the court below erred in its decision on the commerce power.

Congress has not been silent on the subject of strikes in interstate commerce. In the National Labor Relations Act of 1935, 49 Stat. 449, 29 U.S.C. § 151, 29 U.S.C.A. § 151 et seq., as amended by the Labor Management Relations Act, 1947, 61 Stat. 136, 29 U.S.C.(Supp. III) § 141, 29 U.S.C.A. § 141, et seq., Congress safeguarded the exercise by employees of 'concerted activities' and expressly recognized the right to strike.3 It qualified and regulated that right in the 1947 Act. It established certain prerequisites, with which appellants complied, for any strike over contract termination or modification. § 8(d), 29 U.S.C.A. § 158(d). These include notices to both state and federal4 mediation authorities; both did participate in the negotiations in this case. In provisions which did not affect appellants, Congress forbade strikes for certain objectives and detailed procedures for strikes which might create a national emergency. §§ 8(b)(4), 206—210, 29 U.S.C.A. §§ 158(b)(4), 176—180. None of these sections can be read as permitting concurrent state regulation of peaceful strikes for higher wages. Congress occupied this field and closed it to state regulation. Plankinton Packing Co. v. Wisconsin Board, 1950, 338 U.S. 953, 70 S.Ct. 491; LaCrosse Telephone Corp. v. Wisconsin Board, 1949, 336 U.S. 18, 69 S.Ct. 379; Bethlehem Steel Co. v. New York Labor Board, 1947, 330 U.S. 767, 67 S.Ct. 1026, 91 L.Ed. 1234; Hill v. State of Florida ex rel. Watson, 1945, 325 U.S. 538, 65 S.Ct. 1373, 89 L.Ed. 1782.

Even if some state legislation in this area could be sustained, the particular statute before us could not stand. For it conflicts with the federal Act. The Michigan law calls for a notice given 'In the event the parties * * * are unable to settle any dispute' to be followed by mediation, and if that is unsuccessful, by a strike vote within twenty days, with a majority required to authorize a strike. Under the federal legislation, the prescribed strike notice can be given sixty days before the contract termination or modification. § 8(d). The federal Act thus permits strikes at a different and usually earlier time than the Michigan law; and it does not require majority authorization for any strike. This requirement of approval by a majority of the employees was contained in the Bill which passed the House of Representatives;5 but the Act as finally adopted deliberately refrains from imposing the prerequisite of majority approval in each of its references to strike votes. §§ 203(c), 209(b)—210, 29 U.S.C.A. §§ 173(c), 179(b)—180.

Finally, the bargaining unit established in accordance with federal law may be inconsistent with that required by state regulation. Though the unit for the Michigan strike vote cannot extend beyond the State's borders, the unit for which appellant union is the federally certified bargaining representative includes Chrysler plants in California and Indiana as well as Michigan. Chrysler Corp., 42 N.L.R.B. 1145 (1942). Without question, the Michigan provision conflicts with the exercise of federally protected labor rights. A state statute so at war with federal law cannot survive. Plankinton Packing Co. v. Wisconsin Board, 1950, 338 U.S. 953, 70 S.Ct. 491; LaCrosse Telephone Corp. v. Wisconsin Board, 1949, 336 U.S. 18, 69 S.Ct. 379; Bethlehem Steel Co. v. New York Labor Board, 1947, 330 U.S. 767, 67 S.Ct. 1026, 91 L.Ed. 1234; Hill v. State of Florida ex rel. Watson, 1945, 325 U.S. 538, 65 S.Ct. 1373, 89 L.Ed. 1782.

International Union, U.A.W., A.F. of L. Local 232 v. Wisconsin Board, 1949, 336 U.S. 245, 69 S.Ct. 516, upon which Michigan principally relies, was not concerned with a traditional, peaceful strike for higher wages. The employees' conduct there was 'a new technique for bringing pressure upon the employer', a 'recurrent or intermittent unannounced stoppage of work to win unstated ends.' 336 U.S. at pages 249, 264, 69 S.Ct. at pages 519, 527. That activity we regarded as 'coercive,' similar to the sit-down strike held to fall outside the protection of the federal Act in National Labor Relations Board v. Fansteel Metallurgical Corp., 1939, 306 U.S. 240, 59 S.Ct. 490, 83 L.Ed. 627, 123 A.L.R. 599, and to the labor violence held to be subject to state police control in Allen-Bradley Local No. 1111 v. Wisconsin Board, 1942, 315 U.S. 740, 62 S.Ct. 820, 86 L.Ed. 1154. In the Wisconsin Auto Workers case, we concluded that the union tactic was 'neither forbidden by Federal statute nor was it legalized and approved thereby.' 336 U.S. at page 265, 69 S.Ct. at page 527. 'There is no existing or possible conflict or overlapping between the authority of the federal and state Boards, because the federal Board has no authority either to investigate, approve or forbid the union conduct in question. This conduct is governable by the state or it is entirely ungoverned.' 336 U.S. at page 254, 69 S.Ct. at page 521. Clearly, we reaffirmed the principle that if 'Congress has protected the union conduct which the state has forbidden * * * the state legislation must yield.' 336 U.S. at page 252, 69 S.Ct. at page 520. That principle is controlling here.

Reversed.

Mr. Justice DOUGLAS concurs in the result.