Opinion of the Court. 330 U.S. Act, § 29, before and after 1931 amendment, 39 Stat. 490, 46 Stat. 1465, 7 U. S. C. § 269. Our question is primarily one of the construction to be put on the Federal Act. It long has been the rule that exclusion of state action may be implied from the nature of the legislation and the subject matter although express declaration of such result is wanting. Napier v. Atlantic Coast Line R. Co., 272 U. S. 605. In determining whether exclusion of state power will or will not be implied, we well may consider the respective relation of federal and state power to the general subject matter as illustrated by the case in hand. These companies are authorized to do business in New York State, they operate large manufacturing plants in that state, they draw their labor supply from its residents, and the impact of industrial strife in their plants is immediately felt by state police, welfare and other departments. Their labor relations are primarily of interest to the state, are within its competence legally and practically to regulate, and until recently were left entirely to state control. Thus, the subject matter is not so "intimately blended and intertwined with responsibilities of the national government" that its nature alone raises an inference of exclusion. Cf. Hines v. Davidowitz, 312 U. S. 52, 66. Indeed, the subject matter is one reachable, and one which Congress has reached, under the federal commerce power, not because it is interstate commerce but because under the doctrine given classic expression in the Shreveport case, Congress can reach admittedly local and intrastate activities "having such a close and substantial relation to interstate traffic that the control is essential or appropriate to the security of that traffic, to the efficiency of the interstate service, and to the maintenance of conditions under which interstate commerce may be conducted upon fair terms and without molestation or hindrance." 767 Opinion of the Court. Houston & Texas Ry. v. United States, 234 U. S. 342, 351. See also National Labor Relations Board v. Fainblatt, 306 U.S. 601. In the National Labor Relations Act, Congress has sought to reach some aspects of the employer-employee relation out of which such interferences arise. It has dealt with the subject or relationship but partially, and has left outside of the scope of its delegation other closely related matters. Where it leaves the employer-employee relation free of regulation in some aspects, it implies that in such matters federal policy is indifferent, and since it is indifferent to what the individual of his own volition may do we can only assume it to be equally indifferent to what he may do under the compulsion of the state. Such was the situation in Allen-Bradley Local v. Board, 315 U. S. 740, where we held that employee and union conduct over which no direct or delegated federal power was exerted by the National Labor Relations Act is left open to regulation by the state. However, the power of the state may not so deal with matters left to its control as to stand “as an obstacle to the accomplishment and execution of the full purposes and objectives of Congress." Hill v. Florida, 325 U. S. 538, 542. Cf. Maurer v. Hamilton, 309 U. S. 598. When Congress has outlined its policy in rather general and inclusive terms and delegated determination of their specific application to an administrative tribunal, the mere fact of delegation of power to deal with the general matter, without agency action, might preclude any state action if it is clear that Congress has intended no regulation except its own. OregonWashington Co. v. Washington, 270 U. S. 87. In other cases, Congress has passed statutes which initiate regulation of certain activities, but where effective regulation must wait upon the issuance of rules by an administrative body. In the interval before those rules are established, Opinion of the Court. 330 U.S. this Court has usually held that the police power of the state may be exercised. Northwestern Bell Telephone Co. v. Nebraska State Commission, 297 U. S. 471; Welch Co. v. New Hampshire, 306 U. S. 79. But when federal administration has made comprehensive regulations effectively governing the subject matter of the statute, the Court has said that a state regulation in the field of the statute is invalid even though that particular phase of the subject has not been taken up by the federal agency. Napier v. Atlantic Coast Line R. Co., 272 U. S. 605. However, when federal administrative regulation has been slight under a statute which potentially allows minute and multitudinous regulation of its subject, cf. Atlantic Coast Line R. Co. v. Georgia, 234 U. S. 280, or even where extensive regulations have been made, if the measure in question relates to what may be considered a separable or distinct segment of the matter covered by the federal statute and the federal agency has not acted on that segment, the case will be treated in a manner similar to cases in which the effectiveness of federal supervision awaits federal administrative regulation, Northwestern Bell Telephone Co. v. Nebraska State Commission, supra; Welch Co. v. New Hampshire, supra. The states are in those cases permitted to use their police power in the interval. Terminal Railroad Assn. v. Brotherhood of Railroad Trainmen, 318 U. S. 1. However, the conclusion must be otherwise where failure of the federal officials affirmatively to exercise their full authority takes on the character of a ruling that no such regulation is appropriate or approved pursuant to the policy of the statute. Napier v. Atlantic Coast Line, 272 U. S. 605; compare Oregon-Washington Co. v. Washington, 270 U. S. 87, with Parker v. Brown, 317 U. S. 341; cf. Mintz v. Baldwin, 289 U. S. 346. It is clear that the failure of the National Labor Relations Board to entertain foremen's petitions was of the 767 Opinion of the Court. latter class. There was no administrative concession that the nature of these appellants' business put their employees beyond reach of federal authority. The Board several times entertained similar proceedings by other employees whose right rested on the same words of Congress. Neither did the National Board ever deny its own jurisdiction over petitions because they were by foremen. Soss Manufacturing Co., 56 N. L. R. B. 348. It made clear that its refusal to designate foremen's bargaining units was a determination and an exercise of its discretion to determine that such units were not appropriate for bargaining purposes. Maryland Drydock Co., 49 N. L. R. B. 733. We cannot, therefore, deal with this as a case where federal power has been delegated but lies dormant and unexercised. Comparison of the State and Federal statutes will show that both governments have laid hold of the same relationship for regulation, and it involves the same employers and the same employees. Each has delegated to an administrative authority a wide discretion in applying this plan of regulation to specific cases, and they are governed by somewhat different standards. Thus, if both laws are upheld, two administrative bodies are asserting a discretionary control over the same subject matter, conducting hearings, supervising elections and determining appropriate units for bargaining in the same plant. They might come out with the same determination, or they might come out with conflicting ones as they have in the past. Cf. Matter of Creamery Package Mfg. Co., 34 N. L. R. B. 108; Wisc. Emp. Rel. Bd. Case III, No. 348 E-117. But the power to decide a matter can hardly be made dependent on the way it is decided. As said by Mr. Justice Holmes for the Court, "When Congress has taken the particular subjectmatter in hand coincidence is as ineffective as opposi 741700 0-47-53 Opinion of the Court. 330 U.S. tion . . Charleston R. Co. v. Varnville Co., 237 U.S. 597, 604. See also Southern Railway Co. v. Railroad Commission of Indiana, 236 U. S. 439, 448; Missouri Pacific R. R. v. Porter, 273 U. S. 341, 345-6. If the two boards attempt to exercise a concurrent jurisdiction to decide the appropriate unit of representation, action by one necessarily denies the discretion of the other. The second to act either must follow the first, which would make its action useless and vain, or depart from it, which would produce a mischievous conflict. The State argues for a rule that would enable it to act until the federal board had acted in the same case. But we do not think that a case by case test of federal supremacy is permissible here. The federal board has jurisdiction of the industry in which these particular employers are engaged and has asserted control of their labor relations in general. It asserts, and rightfully so, under our decision in the Packard case, supra, its power to decide whether these foremen may constitute themselves a bargaining unit. We do not believe this leaves room for the operation of the state authority asserted. The National and State Boards have made a commendable effort to avoid conflict in this overlapping state of the statutes. We find nothing in their negotiations, however, which affects either the construction of the federal statute or the question of constitutional power insofar as they are involved in this case, since the National Board made no concession or delegation of power to deal with this subject. The election of the National Board to decline jurisdiction in certain types of cases, for budgetary or other reasons presents a different problem which we do not now decide. We therefore conclude that it is beyond the power of New York State to apply its policy to these appellants as |