opinion: UNITED STEELWORKERS OF AMERICA v. WARRIOR & GULF NAVIGATION CO.
  No. 443.
  Argued April 27, 1960.
  Decided June 20, 1960.
  David E. Feller argued the cause for petitioner. With him on the brief were Arthur J. Goldberg, Elliot Bredhoff, James P. Clowes and Carney M. Layne.
  Samuel Lang argued the cause for respondent. With him on the brief were Richard C. Keenan and T. K. Jackson, Jr.
  Opinion of the Court by
  Mr. Justice Douglas,
  announced by Mr. Justice Brennan.
  Respondent transports steel and steel products by barge and maintains a terminal at Chickasaw, Alabama, where it performs maintenance and repair work on its barges. The employees at that terminal constitute a bargaining unit covered by a collective bargaining agreement negotiated by petitioner union. Respondent between 1956 and 1958 laid off some employees, reducing the bargaining unit from 42 to 23 men. This reduction was due in part to respondent contracting maintenance work, previously done by its employees, to other companies. The latter used respondent’s supervisors to lay out the work and hired some of the laid-off employees of respondent (at reduced wages). Some were in fact assigned to work on respondent’s barges. A number of employees signed a grievance which petitioner presented to respondent, the grievance reading:
  “We are hereby protesting the Company’s actions, of arbitrarily and unreasonably contracting out work to other concerns, that could and previously has been performed by Company employees.
  “This practice becomes unreasonable, unjust and discriminatory in lieu [sic] of the fact that at present there are a number of employees that have been laid off for about 1 and % years or more for allegedly lack of work.
  “Confronted with these facts we charge that the Company is in violation of the contract by inducing a partial lock-out, of a number of the employees who would otherwise be working were it not for this unfair practice.”
  The collective agreement had both a “no strike” and a “no lockout” provision. It also had a grievance procedure which provided in relevant part as follows:
  “Issues which conflict with any Federal statute in its application as established by Court procedure or matters which are strictly a function of management shall not be subject to arbitration under this section.
  “Should differences arise between the Company and the Union or its members employed by the Company as to the meaning and application of the provisions of this Agreement, or should any local trouble of any kind arise, there shall be no suspension of work on account of such differences but an earnest effort shall be made to settle such differences immediately in the following manner:
  “A. For Maintenance Employees:
  “First, between the aggrieved employees, and the Foreman involved;
  “Second, between a member or members of the Grievance Committee designated by the Union, and the Foreman and Master Mechanic.
  “Fifth, if agreement has not been reached the matter shall be referred to an impartial umpire for decision. The parties shall meet to decide on an umpire acceptable to both. If no agreement on selection of an umpire is reached, the parties shall jointly petition the United States Conciliation Service for suggestion of a list of umpires from which selection will be made. The decision of the umpire shall be final.”
  Settlement of this grievance was not had and respondent refused arbitration. This suit was then commenced by the union to compel it.
  The District Court granted respondent’s motion to dismiss the complaint. 168 F. Supp. 702. It held after hearing evidence, much of which went to the merits of the grievance, that the agreement did not “confide in an arbitrator the right to review the defendant’s business judgment in contracting out work.” Id., at 705. It further held that “the contracting out of repair and maintenance work, as well as construction work, is strictly a function of management not limited in any respect by the labor agreement involved here.” Ibid. The Court of Appeals affirmed by a divided vote, 269 F. 2d 633, the majority holding that the collective agreement had withdrawn from the grievance procedure “matters which are strictly a function of management” and that contracting out fell in that exception. The case is here on a writ of certiorari. 361 U. S. 912.
  We held in Textile Workers v. Lincoln Mills, 353 U. S. 448, that a grievance arbitration provision in a collective agreement could be enforced by reason of § 301 (a) of the Labor Management Relations Act and that the policy to be applied in enforcing this type of arbitration was that reflected in our national labor laws. Id., at 456-457. The present federal policy is to promote industrial stabilization through the collective bargaining agreement. Id., at 453-454. A major factor in achieving industrial peace is the inclusion of a provision for arbitration of grievances in the collective bargaining agreement.
  Thus the run of arbitration cases, illustrated by Wilko v. Swan, 346 U. S. 427, becomes irrelevant to our problem. There the choice is between the adjudication of cases or controversies in courts with established procedures or even special statutory safeguards on the one hand and the settlement of them in the more informal arbitration tribunal on the other. In the commercial case, arbitration is the substitute for litigation. Here arbitration is the substitute for industrial strife. Since arbitration of labor disputes has quite different functions from arbitration under an ordinary commercial agreement, the hostility evinced by courts toward arbitration of commercial agreements has no place here. For arbitration of labor disputes under collective bargaining agreements is part and parcel of the collective bargaining process itself.
  The collective bargaining agreement states the rights and duties of the parties. It is more than a contract; it is a generalized code to govern a myriad of cases which the draftsmen cannot wholly anticipate. See Shulman, Reason, Contract, and Law in Labor Relations, 68 Harv. L. Rev. 999, 1004-1005. The collective agreement covers the whole employment relationship. It calls into being a new common law — the common law of a particular industry or of a particular plant. As one observer has put it:
  . . [I] t is not unqualifiedly true that a collective-bargaining agreement is simply a document by which the union and employees have imposed upon management limited, express restrictions of its otherwise absolute right to manage the enterprise, so that an employee’s claim must fail unless he can point to a specific contract provision upon which the claim is founded. There are too many people, too many problems, too many unforeseeable contingencies to make the words of the contract the exclusive source of rights and duties. One cannot reduce all the rules governing a community like an industrial plant to fifteen or even fifty pages. Within the sphere of collective bargaining, the institutional characteristics and the governmental nature of the collective-bargaining process demand a common law of the shop which implements and furnishes the context of the agreement. We must assume that intelligent negotiators acknowledged so plain a need unless they stated a contrary rule in plain words.”
  A collective bargaining agreement is an effort to erect a system of industrial self-government. When most parties enter into contractual relationship they do so voluntarily, in the sense that there is no real compulsion to deal with one another, as opposed to dealing with other parties. This is not true of the labor agreement. The choice is generally not between entering or refusing to enter into a relationship, for that in all probability preexists the negotiations. Rather it is between having that relationship governed by an agreed-upon rule of law or leaving each and every matter subject to a temporary resolution dependent solely upon the relative strength, at any given moment, of the contending forces. The mature labor agreement may attempt to regulate all aspects of the complicated relationship, from the most crucial to the most minute over an extended period of time. Because of the compulsion to reach agreement and the breadth of the matters covered, as well as the need for a fairly concise and readable instrument, the product of negotiations (the written document) is, in the words of the late Dean Shulman, “a compilation of diverse provisions: some provide objective criteria almost automatically applicable; some provide more or less specific standards which require reason and judgment in their application; and some do little more than leave problems to future consideration with an expression of hope and good faith.” Shulman, supra, at 1005. Gaps may be left to be filled in by reference to the practices of the particular industry and of the various shops covered by the agreement. Many of the specific practices which underlie the agreement may be unknown, except in hazy form, even to the negotiators. Courts and arbitration in the context of most commercial contracts are resorted to because there has been a breakdown in the working relationship of the parties; such resort is the unwanted exception. But the grievance machinery under a collective bargaining agreement is at the very heart of the system of industrial self-government. Arbitration is the means of solving the unforeseeable by molding a system of private law for all the problems which may arise and to provide for their solution in a way which will generally accord with the variant needs and desires of the parties. The processing of disputes through the grievance machinery is actually a vehicle by which meaning and content are given to the collective bargaining agreement.
  Apart from matters that the parties specifically exclude, all of the questions on which the parties disagree must therefore come within the scope of the grievance and arbitration provisions of the collective agreement. The grievance procedure is, in other words, a part of the continuous collective bargaining process. It, rather than a strike, is the terminal point of a disagreement.
  The labor arbitrator performs functions which are not normal to the courts; the considerations which help him fashion judgments may indeetl be foreign to the competence of courts.
  "A proper conception of the arbitrator’s function is basic. He is not a public tribunal imposed upon the parties by superior authority which the parties are obliged to accept. He has no general charter to administer justice for a community which transcends the parties. He is rather part of a system of self-government created by and confined to the parties. . . .” Shulman, supra, at 1016.
  The labor arbitrator’s source of law is not confined to the express provisions of the contract, as the industrial common law — the practices of the industry and the shop — is equally a part of the collective bargaining agreement although not expressed in it. The labor arbitrator is usually chosen because of the parties’ confidence in his knowledge of the common law of the shop and their trust in his personal judgment to bring to bear considerations which are not expressed in the contract as criteria for judgment. The parties expect that his judgment of a particular grievance will reflect not only what the contract says but, insofar as the collective bargaining agreement permits, such factors -as the effect upon productivity of a particular result, its consequence to the morale of the shop, his judgment whether tensions will be heightened or diminished. For the parties’ objective in using the arbitration process is primarily to further their common goal of uninterrupted production under the agreement, to make the agreement serve their specialized needs. The ablest judge cannot be expected to bring the same experience and competence to bear upon the determination of a grievance, because he cannot be similarly informed.
  The Congress, however, has by § 301 of the Labor Management Relations Act, assigned the courts the duty of determining whether the reluctant party has breached his promise to arbitrate. For arbitration is a matter of contract and a party cannot be required to submit to arbitration any dispute which he has not agreed so to submit. Yet, to be consistent with congressional policy in favor of settlement of disputes by the parties through the machinery of arbitration, the judicial inquiry under § 301 must be strictly confined to the question whether the reluctant party did agree to arbitrate the grievance or did agree to give the arbitrator power to make the award he made. An order to arbitrate the particular grievance should not be denied unless it may be said with positive assurance that the arbitration clause is not susceptible of an interpretation that covers the asserted dispute. Doubts should be resolved in favor of coverage.
  We do not agree with the lower courts that contracting-out grievances were necessarily excepted from the grievance procedure of this agreement. To be sure, the agreement provides that “matters which are strictly a function of management shall not be subject to arbitration.” But it goes on to say that if “differences” arise or if “any local trouble of any kind” arises, the grievance procedure shall be applicable.
  Collective bargaining agreements regulate or restrict the exercise of management functions; they do not oust management from the performance of them. Management hires and fires, pays and promotes, supervises and plans. All these are part of its function, and absent a collective bargaining agreement, it may be exercised freely except as limited by public law and by the willingness of employees to work under the particular, unilaterally imposed conditions. A collective bargaining agreement may treat only with certain specific practices, leaving the rest to management but subject to the possibility of work stoppages. When, however, an absolute no-strike clause is included in the agreement, then in a very real sense everything that management does is subject to the agreement, for either management is prohibited or limited in the action it takes, or if not, it is protected from interference by strikes. This comprehensive reach of the collective bargaining agreement does not mean, however, that the language, “strictly a function of management,” has no meaning.
  “Strictly a function of management” might be thought to refer to any practice of management in which, under particular circumstances prescribed by the agreement, it is permitted to indulge. But if courts, in order to determine arbitrability, were allowed to determine what is permitted and what is not, the arbitration clause would be swallowed up by the exception. Every grievance in a sense involves a claim that management has violated some provision of the agreement.
  Accordingly, “strictly a function of management” must be interpreted as referring only to that over which' the contract gives management complete control and unfettered discretion. Respondent claims that the contracting out of work falls within this category. Contracting out work is the basis of many grievances; and that type of claim is grist in the mills of the arbitrators. A specific collective bargaining agreement may exclude contracting out from the grievance procedure. Or a written collateral agreement may make clear that contracting out was not a matter for arbitration. In such a case a grievance based solely on contracting out would not be arbitra-ble. Here, however, there is no such provision. Nor is there any showing that the parties designed the phrase “strictly a function of management” to encompass any and all forms of contracting out. In the absence of any express provision excluding a particular grievance from arbitration, we think only the most forceful evidence of a purpose to exclude the claim from arbitration can prevail, particularly where, as here, the exclusion clause is vague and the arbitration clause quite broad. Since any attempt by a court to infer such a purpose necessarily comprehends the merits, the court should view with suspicion an attempt to persuade it to become entangled in the construction of the substantive provisions of a labor agreement, even through the back door of interpreting the arbitration clause, when the alternative is to utilize the services of an arbitrator.
  The grievance alleged that the contracting out was a violation of the collective bargaining agreement. There was, therefore, a dispute “as to the meaning and application of the provisions of this Agreement” which the parties had agreed would be determined by arbitration.
  The judiciary sits in these cases to bring into operation an arbitral process which substitutes a regime of peaceful settlement for the older regime of industrial conflict. Whether contracting out in the present case violated the agreement is the question. It is a question for the arbiter, not for the courts.
  Reversed
  Mr. Justice Frankfurter concurs in the result.
  Mr. Justice Black took no part in the consideration or decision of this case.
  [For opinion of Mr. Justice Brennan, joined by Mr. Justice Frankfurter and Mr. Justice Harlan, see ante, p. 569.]
  Section 301 (a) of the Labor Management Relations Act, 1947, 61 Stat. 156, 29 U. S. C. § 185 (a), provides:
  “Suits for violation of contracts between an employer and a labor organization representing employees in an industry affecting commerce as defined in this Act, or between any such labor organizations, may be brought in any district court of the United States having jurisdiction of the parties, without respect to the amount in controversy or without • regard to the citizenship of the parties.” See Textile Workers v. Lincoln Mills, 353 U. S. 448.
  Note 1, supra.
  In § 8 (d) of the National Labor Relations Act, as amended by the 1947 Act, 29 U. S. C. § 158 (d), Congress indeed provided that where there was a collective agreement for a fixed term the duty to bargain did not require either party “to discuss or agree to any modification of the terms and conditions contained in” the contract. And see Labor Board v. Sands Mfg. Co., 306 U. S. 332.
  Complete effectuation of the federal policy is achieved when the agreement contains both an arbitration provision for all unresolved grievances and an absolute prohibition of strikes, the arbitration agreement being the “quid pro quo” for the agreement not to strike. Textile Workers v. Lincoln Mills, 353 U. S. 448, 455.
  “Contracts which ban strikes often provide for lifting the ban under certain conditions. Unconditional pledges against strikes are, however, somewhat more frequent than conditional ones. Where conditions are attached to no-strike pledges, one or both of two approaches may be used: certain subjects may be exempted from the scope of the pledge, or the pledge may be lifted after certain procedures are followed by the union. (Similar qualifications may be made in pledges against lockouts.)
  “Most frequent conditions for lifting no-strike pledges are: (1) The occurrence of a deadlock in wage reopening negotiations; and (2) violation of the contract, especially non-compliance with the grievance procedure and failure to abide by an arbitration award.
  “No-strike pledges may also be lifted after compliance with specified procedures. Some contracts permit the union to strike after the grievance procedure has been exhausted without a settlement, and where arbitration is not prescribed as the final recourse. Other contracts permit a strike if mediation efforts fail, or after a specified cooling-off period.” Collective Bargaining, Negotiations and Contracts, Bureau of National Affairs, Inc., 77:101.
  Cox, Reflections Upon Labor Arbitration, 72 Harv. L. Rev. 1482, 1498-1499 (1959).
  It is clear that under both the agreement in this case and that involved in American Manufacturing Co., ante, p. 564, the question of arbitrability is for the courts to decide. Cf. Cox, Reflections Upon Labor Arbitration, 72 Harv. L. Rev. 1482, 1508-1509. Where the assertion by the claimant is that the parties excluded from court determination not merely the decision of the merits of the grievance but also the question of its arbitrability, vesting power to make both decisions in the arbitrator, the claimant must bear the burden of a clear demonstration of that purpose.
  See Celanese Corp. of America, 33 Lab. Arb. Rep. 925, 941 (1959), where the arbiter in a grievance growing out of contracting out work said:
  “In my research I have located 64 published decisions which have been concerned with this issue covering a wide range of factual situations but all of them with the common characteristic — i. e., the contracting-out of work involved occurred under an Agreement that contained no provision that specifically mentioned contracting-out of work.”
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