delivered the opinion of the Court.

This is a suit brought in the Nebraska courts by employees of the Union Pacific Railroad Co. against that company and labor organizations representing various groups of employees of the railroad to enjoin the application and enforcement of a union shop agreement entered into between the railroad company and the labor organizations. Plaintiffs are not members of any of the defendant labor organizations and desire not to join. Under the terms of the union shop agreement all employees of the railroad, as a condition of their continued employment, must become members of the specified union within 60 days and thereafter maintain that membership. It is alleged that failure on their part to join the union will mean the loss of their employment together with seniority, retirement, pension, and other rights.

*228The employees claim that the union shop agreement violates the “right to work” provision of the Nebraska Constitution (Art. XV, § 13), which provides: 1

“No person shall be denied employment because of membership in or affiliation with, or resignation or expulsion from a labor organization or because of refusal to join or affiliate with a labor organization; nor shall any individual or corporation or association of any kind enter into any contract, written or oral, to exclude persons from employment because of membership in or nonmembership in a labor organization.”

They ask for an injunction restraining the railroad company from enforcing and applying the union shop agreement.

The answers deny that the Nebraska Constitution and laws control and allege that the union shop agreement is authorized by § 2, Eleventh of the Railway Labor Act, as amended, 64 Stat. 1238, 45 U. S. C. § 152, Eleventh, which provides that, notwithstanding the law of “any State,” a carrier and a labor organization may make an agreement requiring all employees within a stated time to become members of the labor organization, provided there is no discrimination against any employee and pro*229vided that membership is not denied nor terminated “for any reason other than the failure of the employee to tender the periodic dues, initiation fees, and assessments (not including fines and penalties) uniformly required as a condition of acquiring or retaining membership.''2

*230The Nebraska trial court issued an injunction. The Supreme Court of Nebraska affirmed. It held that the union shop agreement violates the First Amendment in that it deprives the employees of their freedom of association and violates the Fifth Amendment in that it requires the members to pay for many things besides the cost of collective bargaining. The Nebraska Supreme Court, therefore, held that there is no valid federal law to supersede the “right to work” provision of the Nebraska Constitution. 160 Neb. 669, 71 N. W. 2d 526. The case is here by appeal. 28 U. S. C. § 1257 (1) and (2). We noted probable jurisdiction. 350 U. S. 910.

*231The union shop 3 provision of the Railway Labor Act was written into the law in 1951. Prior to that date the Railway Labor Act prohibited union shop agreements. 48 Stat. 1186, 45 U. S. C. § 152, Fourth and Fifth; 40 Op. Atty. Gen. 254. Those provisions were enacted in 1934 when the union shop was being used by employers to establish and maintain company unions, “thus effectively depriving a substantial number of employees of their right to bargain collectively.” S. Rep. No. 2262, 81st Cong., 2d Sess., p. 3. By 1950, company unions in this field had practically disappeared. Id. Between 75 and 80% of railroad employees were members of labor organizations. H. R. Rep. No. 2811, 81st Cong., 2d Sess., p. 4. While nonunion members got the benefits of the collective bargaining of the unions, they bore “no share of the cost of obtaining such benefits.” Id., at 4. As Senator Hill, who managed the bill on the floor of the Senate, said, “The question in this instance is whether those who enjoy the fruits and the benefits of the unions should make a fair contribution to the support of the unions.” 96 Cong. Rec., Pt. 12, p. 16279.

The union shop provision of the Railway Labor Act is only permissive. Congress has not compelled nor required carriers and employees to enter into union shop agreements. The Supreme Court of Nebraska nevertheless took the view that justiciable questions under the First and Fifth Amendments were presented since Congress, by the union shop provision of the Railway Labor *232Act, sought to strike down inconsistent laws in 17 States. Cf. Hudson v. Atlantic Coast Line R. Co., 242 N. C. 650, 89 S. E. 2d 441; Otten v. Baltimore & O. R. Co., 205 F. 2d 58. The Supreme Court of Nebraska said, “Such action on the part of Congress is a necessary part of every union shop contract entered into on the railroads as far as these 17 States are concerned for without it such contracts could not be enforced therein.” 160 Neb., at 698, 71 N. W. 2d, at 547. We agree with that view. If private rights are being invaded, it is by force of an agreement made pursuant to federal law which expressly declares that state law is superseded. Cf. Smith v. Allwright, 321 U. S. 649, 663. In other words, the federal statute is the source of the power and authority by which any private rights are lost or sacrificed.4 Cf. Steele v. Louisville & N. R. Co., 323 U. S. 192, 198-199, 204; Railroad Trainmen v. Howard, 343 U. S. 768; Public Utilities Comm’n v. Pollak, 343 U. S. 451, 462. The enactment of the federal statute authorizing union shop agreements is the governmental action on which the Constitution operates, though it takes a private agreement to invoke the federal sanction.

As already noted, the 1951 amendment, permitting the negotiation of union shop agreements, expressly allows those agreements notwithstanding any law “of any State.” § 2, Eleventh.5 A union agreement made pursuant to the Railway Labor Act has, therefore, the imprimatur of the federal law upon it and, by force of the Supremacy Clause of Article VI of the Constitution, could not be made illegal nor vitiated by any provision of the laws of a State.

*233We come then to the merits.

In the absence of conflicting federal legislation, there can be no doubt that it is within the police power of a State to prohibit the union or the closed shop. We so held in Lincoln Union v. Northwestern Co., 335 U. S. 525, and in American Federation of Labor v. American Sash Co., 335 U. S. 538, against the challenge that local “right to work” laws, including Nebraska’s, violated the requirements of due process. But the power of Congress to regulate labor relations in interstate industries is likewise well-established. Congress has authority to adopt all appropriate measures to “facilitate the amicable settlement of disputes which threaten the service of the necessary agencies of interstate transportation.” Texas & N. O. R. Co. v. Railway Clerks, 281 U. S. 548, 570. These measures include provisions that will encourage the settlement of disputes “by inducing collective bargaining with the true representative of the employees and by preventing such bargaining with any who do not represent them” (Virginian R. Co. v. Federation, 300 U. S. 515, 548), and that will protect the employees against discrimination or coercion which would interfere with the free exercise of their right to self-organization and representation. Labor Board v. Jones & Laughlin, 301 U. S. 1, 33. Industrial peace along the arteries of commerce is a legitimate objective; and Congress has great latitude in choosing the methods by which it is to be obtained.

The choice by the Congress of the union shop as a stabilizing force seems to us to be an allowable one. Much might be said pro and con if the policy issue were before us. Powerful arguments have been made here that the long-run interests of labor would be better served by the development of democratic traditions in trade unionism without the coercive element of the union or the closed shop. Mr. Justice Brandéis, who had wide experience in labor-management relations prior to his appointment to *234the Court, wrote forcefully against the closed shop. He feared that the closed shop would swing the pendulum in the opposite extreme and substitute “tyranny of the employee” for “tyranny of the employer.” 6 But the question is one of policy with which the judiciary has no concern, as Mr. Justice Brandéis would have been the first to concede. Congress, acting within its constitutional powers, has the final say on policy issues. If it acts unwisely, the electorate can make a change. The task of the judiciary ends once it appears that the legislative measure adopted is relevant or appropriate to the constitutional power which Congress exercises. The ingredients of industrial peace and stabilized labor-management relations are numerous and complex. They may well vary from age to age and from industry to industry. What would be needful one decade might be anathema the next. The decision rests with the policy makers, not with the judiciary.

It is said that the right to work, which the Court has frequently included in the concept of “liberty” within the meaning of the Due Process Clauses (see Truax v. Raich, 239 U. S. 33; Takahashi v. Fish & Game Commission, 334 U. S. 410), may not be denied by the Congress. The question remains, however, whether the long-range interests of workers would be better served by one type of *235union agreement or another. That question is germane to the exercise of power under the Commerce Clause— a power that often has the quality of police regulations. See Cleveland v. United States, 329 U. S. 14, 19. One would have to be blind to history to assert that trade unionism did not enhance and strengthen the right to work. See Webb, History of Trade Unionism; Gregory, Labor and the Law. To require, rather than to induce, the beneficiaries of trade unionism to contribute to its costs may not be the wisest course. But Congress might well believe that it would help insure the right to work in and along the arteries of interstate commerce. No more has been attempted here. The only conditions to union membership authorized by § 2, Eleventh of the Railway Labor Act are the payment of “periodic dues, initiation fees, and assessments.” The assessments that may be lawfully imposed do not include “fines and penalties.” The financial support required relates, therefore, to the work of the union in the realm of collective bargaining. No more precise allocation of union overhead to individual members seems to us to be necessary. The prohibition of “fines and penalties” precludes the imposition of financial burdens for disciplinary purposes. If “assessments” are in fact imposed for purposes not germane to collective bargaining,7 a different problem would be presented.

*236Wide-ranged problems are tendered under the First Amendment. It is argued that the union shop agreement forces men into ideological and political associations which violate their right to freedom of conscience, freedom of association, and freedom of thought protected by the Bill of Rights.8 It is said that once a man becomes a *237member of these unions he is subject to vast disciplinary control9 and that by force of the federal Act unions now can make him conform to their ideology.

*238On the present record, there is no more an infringement or impairment of First Amendment rights than there would be in the case of a lawyer who by state law is required to be a member of an integrated bar. It is argued that compulsory membership will be used to impair freedom of expression. But that problem is not presented by this record. Congress endeavored to safeguard against that possibility by making explicit that no conditions to membership may be imposed except as respects “periodic dues, initiation fees, and assessments.” If other conditions are in fact imposed, or if the exaction of dues, initiation fees, or assessments is used as a cover for forcing ideological conformity or other action in contravention of the First Amendment, this judgment will not prejudice the decision in that case. For we pass narrowly on § 2, Eleventh of the Railway Labor Act. We only hold that the requirement for financial support of the collective-bargaining agency by all who receive the benefits of its work is within the power of Congress under the Commerce Clause and does not violate either the First or the Fifth Amendments. We express no opinion on the use of other conditions to secure or maintain membership in a labor organization operating under a union or closed shop agreement.

Reversed.

concurring.

The provision of law now challenged is the latest exercise by Congress of its power under the Commerce Clause to promote peaceful industrial relations in the *239functioning of interstate railroads and thereby to further the national well-being. A mere recital of the course of history in this important field goes a long way to indicate that the main point of attack against the Act of January 10, 1951, 64 Stat. 1238, raises questions not of constitutional validity but of policy in a domain of legislation peculiarly open to conflicting views of policy. These efforts constitute a body of empiric responses by Congress to new problems or new insight for dealing with old problems.

The course of legislation affecting industrial controversies on railroads flows through these statutes: the Act of October 1, 1888, 25 Stat. 501; the Erdman Act of June 1, 1898, 30 Stat. 424, growing out of the Pullman strike of 1894, see In re Debs, 158 U. S. 564; the Newlands Act of July 15, 1913, 38 Stat. 103; the Adamson Law of September 3, 1916, 39 Stat. 721; Title III of the Transportation Act of 1920, 41 Stat. 456, 469; the Railway Labor Act of May 20, 1926, 44 Stat. 577; the Act of June 21, 1934, 48 Stat. 1185, amending the Railway Labor Act.

Nearly fifty years ago, the railroads successfully attacked the constitutionality of a vital feature of the Act of June 1, 1898, whereby Congress made it a criminal offense to bar employment in interstate railroads merely because of labor union membership. Adair v. United States, 208 U. S. 161 (1908). It is fair to say that this decision marks the nadir of denial to Congress of the power to regulate the conditions for assuring the Nation’s dependence on the peaceful and effective operation of its railroads. The criticisms that the case aroused, see, e. g., Richard Olney, Discrimination Against Union Labor— Legal?, 42 Amer. L. Rev. 161 (1908), and Roscoe Pound, Liberty of Contract, 18 Yale L. J. 454 (1909), were reflected in later decisions of the Court. Neither the Commerce Clause nor the Due Process Clause was thereafter conceived, at least so far as they restrain railroad labor *240regulation, to be confined within such doctrinaire and frozen bounds as were confined the assumptions which underlay the decision in the Adair case. Thus, the Court sustained the Adamson Law, which was enacted to avert the threatened nation-wide railroad strike of 1916, Wilson v. New, 243 U. S. 332 (1917); Title III of the Transportation Act of 1920, Pennsylvania R. Co. v. Railroad Labor Board, 261 U. S. 72 (1923); and the Railway Labor Act of 1926, Texas & New Orleans R. Co. v. Brotherhood of Railway & Steamship Clerks, 281 U. S. 548 (1930); but see Railroad Retirement Board v. Alton R. Co., 295 U. S. 330 (1935).

The change in the Court’s understanding of industrial problems, certainly as they affect railroads, in their bearing upon the country’s commerce and all that thereby hangs, to no small degree reflected the changed attitude of the railroads towards the role of railroad labor unions in the discharge of the functions of railroads. As striking evidence as any of this important shift in opinion is the fact that the Railway Labor Act of 1926 came on the statute books through agreement between the railroads and the railroad unions on the need for such legislation. It is accurate to say that the railroads and the railroad unions between them wrote the Railway Labor Act of 1926 and Congress formally enacted their agreement. I doubt whether there is another instance in the history of important legislation in which acknowledgment was so candidly made by a President of the United States that agreement reached between industrial disputants regarding legislation appropriate for securing their peaceful relations should become law. “I am informed,” the President reported to Congress in his annual message of December 8, 1925, “that the railroad managers and their employees have reached a substantial agreement as to what legislation is necessary to regulate and improve their relationship. Whenever they bring for*241ward such proposals, which seem sufficient also to protect the interests of the public, they should be enacted into law.” H. R. Doc. No. 2, 69th Cong., 1st Sess., p. 18. The President was Calvin Coolidge.

We have come full circle from the point of view in the Adair case. There the railroads, to repeat, successfully resisted an Act of Congress which outlawed what colloquially became known as the “yellow-dog contract.” We are now asked to declare it beyond the power of Congress to authorize railroads to enter into voluntary agreements with the unions to which the overwhelming proportion of railway employees belong whereby all their workers are required to belong to such unions, provided, of course, that the unions be open unions, i. e., that membership in the unions be available on ordinary, appropriate terms. It seems to me that the constitutional objections to this legislation were conclusively and compendiously answered by Mr. Justice Holmes in his dissent in Adair v. United States, supra:

“Where there is, or generally is believed to be, an important ground of public policy for restraint the Constitution does not forbid it, whether this court agrees or disagrees with the policy pursued. It cannot be doubted that to prevent strikes, and, so far as possible, to foster its scheme of arbitration, might be deemed by Congress an important point of policy, and I think it impossible to say that Congress might not reasonably think that the provision in question would help a good deal to carry its policy along. But suppose the only effect really were to tend to bring about the complete unionizing of such railroad laborers as Congress can deal with, I think that object alone would justify the act. I quite agree that the question what and how much good labor unions do, is one on which intelligent people may *242differ, — I think that laboring men sometimes attribute to them advantages, as many attribute to combinations of capital disadvantages, that really are due to economic conditions of a far wider and deeper kind — but I could not pronounce it unwarranted if Congress should decide that to foster a strong union was for the best interest, not only of the men, but of the railroads and the country at large.” 208 U. S., at 191-192.

The Court has put to one side situations not now before us for which the protection of the First Amendment was earnestly urged at the bar. I, too, leave them to one side.