While the parties to a collective bargaining agreement may delineate the scope of an arbitration provision according to their design, neither the language of the provision in the instant ease, nor the facts, support the contention that the arbitration procedure excluded the arbitrability of the present grievance of the union. We hold, for the reasons that follow, that the trial court, by accepting the posited contentions of the defendant, improperly resolved the merits of the dispute. Instead of narrowly and exclusively determining the question of arbitrability, the court invaded the province of the arbitrator.
Plaintiff 0 ’Malley is president of, and sues in a representative capacity for, the Oil, Chemical and Atomic Workers International, Union Local 1-128, AFL-CIO (hereinafter termed “union”). Defendant, the Wilshire Oil Company (hereinafter termed “company”) is engaged in the manufacture and processing of petroleum in interstate commerce. Since 1948 the union has been the certified bargaining agent of the company’s employees.
*485In April of 1959 the union and the company entered into a collective bargaining agreement covering wages, hours and working conditions of the company’s employees. Among other matters, the agreement contained a recognition clause, a no-strike clause, and a provision relating to contracting out of work. The agreement established a grievance procedure culminating in arbitration for the resolution of disputes with regard to the agreement.1
In December 1960 the union submitted a grievance, which, in substance, protested the contracting out by the company of some of its transportation work. Subsequently, the company rejected the grievance. The union, pursuant to the established procedure, sought arbitration of the dispute. The company refused to submit the dispute to arbitration. As a result, the union filed a petition for an order directing arbitration.
In its petition the union incorporated by reference the statement of the grievance contained in its letter to the company, which alleged as to contract work the company's violation of article 152 and “any other Article or Articles that may be found to be violated in the process of settling the complaint.” The petition concluded that a dispute therefore existed with regard to “the interpretation and application” of the contract, thereby requiring arbitration.
In its answer to the petition the company relied on language in article 22 of the agreement with respect to arbitration to the effect that: “Under no circumstances may an arbitration decision in any manner nullify, amend, modify, extend, reduce or otherwise change any of the terms or conditions of this Agreement. ...” The company then set out efforts of the union, prior to and after the grievance, to *486modify article 15 in order to include more explicit and stringent limitations upon the company’s right to contract out work. The company contended that since the practice of contracting out transportation work had long been a company policy and since the union’s proposals for its limitation had been rejected at the collective bargaining table, the agreement permitted such policy and the grievance was specifically excluded from arbitration.
The trial court denied the request of the petition, concluding that: “ [Interpreting the Articles of Agreement of April 10, 1959 in accordance with the intentions of the parties as therein expressed and in the light of all of the facts and circumstances surrounding the negotiations for and execution of prior and subsequent agreements, no agreement can be found between Respondent and Petitioner which requires the arbitration of grievances arising out of or based upon the contracting out of transportation work. ’ ’
In the enforcement of provisions of collective bargaining agreements obligating the parties to arbitrate disputes, state courts exercise concurrent jurisdiction with federal courts. (Charles Dowd Box Co. v. Courtney (1962) 368 U.S. 502 [82 S.Ct. 519, 7 L.Ed.2d 483].) In so doing state courts must, however, in adjudicating an action which could have been brought in the federal courts under section 301 of the Labor Management Relations Act, apply federal law. (Local 174 Teamsters, etc. of America v. Lucas Flour Co. (1962) 369 U.S. 95 [82 S.Ct. 571, 7 L.Ed.2d 593].) Since in the instant case the company is engaged in interstate commerce, the parties agree that federal law must necessarily govern.
The wellspring of federal law respecting the enforcement of arbitration agreements consists of three cases decided by the Supreme Court in I960.3 As we shall point out, these decisions, recognizing the special nature of the collective bargaining agreement and the crucial role of the arbitrator in resolving disputes arising under it, narrowly confine the role of the court as contrasted with that of the arbitrator.
We have recently analyzed this trilogy of United States Supreme Court cases in Posner v. Grunwald-Marx, Inc. (1961) 56 Cal.2d 169 [14 Cal.Rptr. 297, 363 P.2d 313], In that case *487we criticized the prior doctrine o£ International Assn. of Machinists v. Cutler-Hammer, Inc. (1947) 271 App. Div. 917 [67 N.Y.S.2d 317]; affd. 297 N.Y. 519 [74 N.E.2d 464], Cutler-Hammer had held that a court could properly reject a petition to arbitrate a matter which, in the court’s view, did not compose an arbitrable issue because petitioner’s asserted interpretation of the contract transgressed the plain meaning of the words.4
In Posner we described and adopted the ruling of the Supreme Court cases; we said: “This rule is to the effect that, where the collective bargaining agreement provides for arbitration of all disputes pertaining to the meaning, interpretation and application of the collective bargaining agreement and its provisions, any dispute as to the meaning, interpretation and application of any specific matter covered by the collective bargaining agreement is a matter for arbitration. Doubts as to whether the arbitration clause applies are to be resolved in favor of coverage. The parties have contracted for an arbitrator’s decision and not for that of the courts.” (56 Cal.2d at p. 175.) Although the issue in Posner did not involve interstate commerce and therefore did not necessarily invoke the federal rule as described by the United States Supreme Court, we nevertheless as a matter of policy followed the federal approach. We held that the trial court, instead of confining itself to the issue of whether the dispute was subject to arbitration, improperly passed upon the merits of the issue.
4We believe the United States Supreme Court eases are dis-positive of the present problem. Thus in United Steelworkers of America v. American Mfg. Co., supra (1960) 363 U.S. 564 [80 S.Ct. 1343, 4 L.Ed.2d 1403], the union brought suit to compel arbitration, under an agreement providing for arbitration of all disputes “as to the meaning, interpretation and application” of the provisions of the agreement. The grievance there related to a contractual pro *488vision that the employer would reemploy and promote employees on the principle of seniority “where ability and efficiency are equal.” An employee left his job due to an injury and while absent brought an action for compensation benefits. The parties settled the case; the employee’s physician indicated that the employee had become 25 per cent “permanently partially disabled.” Two weeks after the settlement the union filed a grievance charging that the employee was entitled to return to his job by virtue of the seniority provision of the collective bargaining agreement. The company refused to arbitrate the grievance; the union filed an action in the United States District Court. Stating that the employee’s acceptance of the settlement estopped him from claiming seniority or employment rights, the District Court rendered a summary judgment against the union.
The Court of Appeals affirmed the District Court on a different basis than that which that court had expressed, holding that the grievance was ‘ ‘ a frivolous, patently baseless one, not subject to arbitration under the collective bargaining agreement.” (P. 566.) The Supreme Court reversed indicating that the Court of Appeals, in becoming embroiled in the merits, had misconstrued the role of the court.
The Supreme Court stated: “The function of the court is very limited when the parties have agreed to submit all questions of contract interpretation to the arbitrator. It is confined to ascertaining whether the party seeking arbitration is making a claim which on its face is governed by the contract. Whether the moving party is right or wrong is a question of contract interpretation for the arbitrator. In these circumstances the moving party should not be deprived of the arbitrator’s judgment, when it was his judgment and all that it connotes that was bargained for. ’ ’ The court concluded: “The courts, therefore, have no business weighing the merits of the grievance, considering whether there is equity in a particular claim, or determining whether there is particular language in the written instrument which will support the claim. The agreement is to submit all grievances to arbitration, not merely those which the court will deem meritorious. The processing of even frivolous claims may have therapeutic values of which those who are not a part of the plant environment may be quite unaware.” (363 U.S. at pp. 567-568 [80 S.Ct. 1343, 1346, 4 L.Ed.2d 1406-1407].)
Without more, the principles above elaborated would *489resolve the instant case. The union has alleged in its petition that the company’s action in contracting out transportation work violates article 15 and may also impliedly violate other provisions of the agreement.5 To the extent that the company’s contentions constitute a denial of the merits of these allegations, judicial consideration is clearly foreclosed.
The company seeks to avoid this result by arguing that the parties excluded this grievance from the arbitration provisions. As already indicated, the company relies on that part of the arbitration provision (article 22) which states: “Under no circumstances may an arbitration decision in any manner nullify, amend, modify, extend, reduce or otherwise change any of the terms or conditions of this Agreement. . . . ” The company describes two attempts of the union to extend the explicit coverage of article 15; the first transpired when the provision was adopted in 1950 and the second in 1961, subsequent to the present grievance. The position of the company appears to be that the bargaining history with respect to article 15 indicates that the union now seeks a “modification” of the agreement and that the parties have specifically prohibited the arbitrator from effecting any such modification.
An analysis of this contention requires consideration of the second decision of the 1960 trilogy, United Steelworkers of America v. Warrior & Gulf Navigation Co., supra (1960) 363 U.S. 574 [80 S.Ct. 1347, 4 L.Ed.2d 1409], The grievance there, similarly, involved the employer’s right to contract out work previously performed by its employees. The employer, Warrior & Gulf Navigation Co., maintained a terminal for the performance of maintenance and repair work on barges used in its business of transporting steel and steel products. It had laid off a number of employees, due in part to the contracting out of maintenance work which had previously been performed by its employees. The companies with which it had contracted out the performance of the work utilized *490Warrior & Gulf’s supervisors to oversee the work, and hired, at reduced wages, some of the laid-oif employees. The union brought a grievance objecting to Warrior & Gulf’s actions. The company refused to arbitrate, relying upon a provision in the collective bargaining agreement to the effect that “matters which are strictly a function of management” were not subject to arbitration. It contended that contracting out was a “function of management” and the parties had thereby excluded such a grievance from arbitration.
In rejecting this contention, the Supreme Court called attention to the unique nature of the collective bargaining contract and to the vital and dynamic role of the arbitrator in the area of industrial relations. 6 The majority opinion of Justice Douglas sets forth: “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. . . . A collective bargaining agreement is an effort to erect a system of industrial self-government. . . . [T]he 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.” (363 U.S. at pp. 578-581 [80 S.Ct. 1351-1352, 4 L.Ed.2d 1414-1417].)
This analysis led the Supreme Court to conclude: “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 colleetr"”bargaining process. It, rather than a strike, is the terminal point of a disagreement.” (363 U.S. at p. 581 [80 S.Ct. 1352, 4 L.Ed.2d 1417].)
Arbitration is, of course, a matter of contract, and the parties may freely delineate the area of its application.
*491The court’s role, according to the Supreme Court, however, must be strictly limited to a determination of whether the party resisting arbitration agreed to arbitrate. A heavy presumption weighs the scales in favor of arbitrability; an order directing arbitration should be granted “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.” (363 U.S. at pp. 582-583 [80 S.Ct. 1353, 4 L.Ed.2d 1417-1418].)
Applying these principles the Supreme Court observed; “. . . 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.” (363 U.S. at p. 584 [80 S.Ct. 1354, 4 L.Ed.2d 1418] ; emphasis added.)
The Supreme Court then held the arbitration clause covered the grievance as to contracting out. “. . . 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 arbitrable. 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 use the services of an arbitrator.” (363 U.S. at pp. 584-585 [80 S.Ct. 1354, 4 L.Ed.2d 1418-1419] ; emphasis added.)
Subsequent federal decisions have reemphasized the principle of Warrior that the arbitration clause covers the grievance in the absence of manifest exclusion. Thus in Procter *492& Gamble Independent Union v. Procter & Gamble Mfg. Co. (2d Cir. 1962) 298 F.2d 644, 645-646, the court said: “The nub of the matter is that under the broad and comprehensive standard labor arbitration clause every grievance is arbitrable, unless the provisions of the collective bargaining agreement concerning grievances and arbitration contain some clear and unambiguous clause of exclusion, or there is some other term of the agreement that indicates beyond peradventure of doubt that a grievance concerning a particular matter is not intended to be covered by the grievance and arbitration procedure set forth in the agreement.”
In Taft Broadcasting Co. v. Radio Broadcast Technicians Local Union No. 253 (5th Cir. 1962) 298 F.2d 707, 709, the Court likewise stated, “Two principles are emphasized. First, the purpose to exclude a particular type of dispute from the arbitration promise must be clearly spelled out. And second, courts must overcome the temptation of passing on the intrinsic merits of the controversy under the guise of determining whether the dispute is within the promise to arbitrate.” (See also Association of Westinghouse Salaried Emp. v. Westinghouse Electric Corp. (3d Cir. 1960) 283 F.2d 93; International Assn. of Machinists v. International Aircraft Services, Inc. (4th Cir. 1962) 302 F.2d 808; International Union, U.A.W. v. Cardwell Mfg. Co. (10th Cir. 1962) 304 F.2d 801.)
The company seeks to avoid Warrior by describing alleged elements in the instant case which it considers to be distinguishing factors. First, it argues that the arbitration clause there was broader and the exclusion clause was “vague.” Second, it notes that here, unlike in Warrior, the contract includes a specific clause dealing with contract work. Finally, it relies upon the instant bargaining history with respect to the contract-work provision. We shall explain why we have concluded that the attempted distinctions cannot prevail.
The arbitration provision in Warrior provided for arbitration “Should differences arise ... as to the meaning and application of the provisions of this agreement, or should any local trouble of any kind arise.” The company emphasizes the reference to “local trouble.” The Supreme Court, however, specifically relied upon the language in the provision before it which was essentially the same as that of the instant contract. The court stated: ‘ ‘ The grievance 'alleged that the contracting out was a violation of the collective bar*493gaining 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.” (363 U.S. 574 at p. 585 [80 S.Ct. 1354, 4 L.Ed.2d 1419].)
Any remaining doubt is resolved by the fact that the subsequent federal cases which we have cited supra held that arbitration provisions similar to the present one were of sufficient breadth to invoke the principles of the Warrior decision.
The company’s argument that in Warrior, unlike here, the exclusion clause was “vague” is equally without merit. The instant clause is not only “vague,” but hardly seems to reach the status of an “exclusion” clause. To state that the arbitrator lacks power to amend, modify or otherwise change an agreement is merely to restate explicitly the inherent limitation in the arbitrator’s power to handle grievances relating to the ‘ ‘ application and interpretation of this AgreementIf the provision empowers the arbitrator only to apply and interpret the agreement, he is not authorized to amend it.7
In any event, whatever the company contends as to vagueness, to construe the exclusion clause as the company desires would countenance a full-scale leap into the merits of the dispute in order to construe the limitations of arbitrability. In Association of Westinghouse Salaried Emp. v. Westinghouse Electric Corp. (3d Cir. 1960) 283 F.2d 93, the employer relied upon a similar provision which stated that an arbitrator could not “ [a]dd to, detract from, or in any way alter the provisions of this Agreement. ...” The employer sought to show that the parties had understood a controverted provision to have a particular meaning and that the grievance was therefore excluded from arbitration. The court observed: “This is just the thing which the Supreme Court has told us to avoid.” (283 F.2d at p. 95.)
Although the company heavily stresses Local No. 725, Intl. Union of Operating Engineers v. Standard Oil Co. of Indiana *494(D.C. N.Dak. 1960) 186 F.Supp. 895, the exclusion clause of that contract differed from the instant provision. It stated that: “. . . proposals to add to or change this Agreement shall not be arbitrable and that no proposal to modify, amend or terminate this Agreement, as well as any matter or subject arising out of or in connection with such proposal, may be referred for arbitration. ...” (At p. 897; emphasis added.) The court referred to the bargaining history to determine what “proposals” had been made to give content to this specific exclusion of such “proposals” from arbitration. (See Note “Arbitrability” of Labor Disputes, 47 Va. L.Rev. 1182, 1202 (1961).)
We find no merit in the company’s second point of attempted distinction that the contract before us, unlike that in Warrior, incorporates a specific clause as to contract work. If the courts and the arbitrators can find implied limitations on the power to subcontract,8 it is difficult to see any diminution of such limitations by the fact that the parties have restricted such power in express or particular language. The company here urges in essence an application of the principle of inclusio unius est exclusio alterius. To do so, however, is to overlook the differences between a collective bargaining agreement and a standard commercial contract, and to ignore the Supreme Court’s words of caution against blind application of contractual rules to “a generalized code to govern a myriad of cases which the draftsmen cannot wholly anticipate.” (United Steelworkers of America v. Warrior & Gulf Navigation Co., supra, 363 U.S. 574, 578 [80 S.Ct. 1351, 4 L.Ed.2d 1409,1415].)
The final refuge of the company in the bargaining history of the clause as a distinguishing feature between this case and Warrior overlooks the very holding and purport of Warrior. There the company presented evidence of bargaining history, but the majority opinion of the Supreme Court did not even refer to it. In his dissent Justice Whittaker stressed the fact that the employer had contracted out work since the beginning of its operation 19 years earlier and that the union had repeatedly sought to negotiate limitations of the employer’s power to do so. (363 U.S. 574, 587 [80 S.Ct. 1347, 1355, 4 L.Ed.2d 1409, 1420].) Indeed, the failure of the Supreme Court so much as to consider this history has led some courts and commentators to conclude that consideration *495of bargaining history in the interpretation of the arbitration provision is foreclosed.9
Even if we were to refer to the bargaining history, however, we would do so only to determine the area of the agreement to arbitrate and not the merits of the dispute. The company’s showing here reaches to the latter rather than the former province; the effort fails. As the United States Court of Appeals for the Ninth Circuit points out in Pacific Northwest Bell Tel. Co. v. Communication Workers of America (9th Cir. 1962) 310 F.2d 244, the test is “whether judicial construction of the arbitrability clause would require that the underlying dispute be first resolved in order to determine whether it is subject to arbitration.” (At p. 248.) The essential distinction therefore becomes whether the aim of the presentation is to indicate agreement on the underlying issue or to show that the parties agreed that a particular area was not a subject for arbitration. Only evidence of the latter sort of agreement is admissible under Warrior.
In surveying the bargaining history the court cannot, in determining the question of arbitrability, decide the merits. As the Court of Appeals points out, the court cannot lay hold of the preliminary problem of the province of the arbitrator to reach and resolve the principal question itself. ‘ ‘ Such was the ease in Warrior,” says the Court of Appeals, further declaring: “. . . before the court could find that the dispute was excluded from arbitration, it was necessary to determine whether the company had retained this disputed right as a function of management: the merits of the underlying dispute itself. ’ ’ (310 F.2d at pp. 248-249.)
The bargaining history which the company seeks to present here pertains to the construction of article 15 and not the construction of the agreement to arbitrate. As such, it relates to, and resolves, the merits of the dispute; it is not solely directed to proof of an agreement to exclude a particular subject-matter from arbitration. Consideration of the bargaining history in the present case is, therefore, patently improper.
The Supreme Court’s decision in Warrior thus directly governs the instant issue. The company’s claimed distinguishing factors merely fabricate an elaborate camouflage for entiee*496ment of the court into a resolution of the merits of the dispute. By accepting the invitation, the trial court allowed itself to resolve the merits and thereby to invade the realm of the arbitrator. Yet federal law admittedly governs this ease, and the United States Supreme Court has expressly enjoined determination of the merits of a grievance “under the guise of interpreting the grievance procedure of collective bargaining agreements.” (United Steelworkers of America v. American Mfg. Co., supra (1960) 363 U.S. 564 at p. 569 [80 S.Ct. 1343, 1347, 4 L.Ed.2d 1403, 1407].)
For this reason, we hold that the trial court’s denial of the petition for order directing arbitration was incorrect.
The judgment is reversed.
Gibson, C. J., Traynor, J., Peters, J., and Peek, J., concurred.
The relevant portions of Article 22 relating to grievances are as follows:
“Grievances relating to the application and interpretation of this Agreement shall be handled as follows:
“ (c) If the grievance is not settled as a result of the foregoing, then the Union may . . . request arbitration thereof. . . . Under no circumstances may an arbitration decision in any manner nullify, amend, modify, extend, reduce or otherwise change any of the terms or conditions of this Agreement. ...”
Article 15 provides: “Except for office janitorial services or in case of an emergency the Company shall not employ or otherwise engage contract labor to perform upkeep and repair work normally performed by employees covered by this Agreement until all laid off employees who still retain their rehiring rights . . . have been offered reemployment with the Company. ...”
United Steelworkers of America v. American Mfg. Co., 363 U.S. 564, 569 [80 S.Ct. 1343, 1363, 4 L.Ed.2d 1403, 1432]; United Steelworkers of America v. Warrior & Gulf Navigation Co., 363 U.S. 574 [80 S.Ct. 1347, 4 L.Ed.2d 1409] ; United Steelworkers of America v. Enterprise Wheel & Car Corp., 363 U.S. 593 [80 S.Ct. 1358, 4 L.Ed.2d 1424],
The court’s statement of the doctrine follows: “While the contract provides for arbitration of disputes as to the ‘meaning, performance, nonperformance or application’ of its provisions, the mere assertion by a party of a meaning of a provision which is clearly contrary to the plain meaning of the words cannot make an arbitrable issue. ... If the meaning of the provision of the contract sought to be arbitrated is beyond dispute, there cannot be anything to arbitrate and the contract cannot be said to provide for arbitration.’’ (International Assn.of Machinists v. Cutler-Hammer, Inc., 271 App.Div. 917 [67 N.Y.S.2d 317, 318], affd. 297 N.Y. 519 [74 N.E.2d 464].)
Implied limitations arising from provisions of a collective bargaining agreement [such as recognition of seniority] have been found by both the courts and the arbitrators. These limitations have been enforced even where the agreement in no way expressly limited the employer’s power to contract out. See United Steelworkers v. Warrior & Gulf Navigation Co., supra, for recognition of the power of the arbitrator to find such an implied limitation. In International Union, U.A.W. v. Webster Elec. Co. (7th Cir. 1962) 299 F.2d 195, the court sustained a declaratory judgment finding an implied limitation as to contracting out. See also Cox, Reflections Upon Labor Arbitration (1959) 72 Harv.L.Rev. 1482, 1497, 1517; 60 Mich. L. Rev. 1173 (1962).
For enlightened discussion of the nature of the collective bargaining agreement and the role of the arbitrator, see Shulman, Beacon, Contract, and Law in Labor Relations, 68 Harv.L.Rev. 999 (1955) ; Cox, Reflections Upon Labor Arbitration, 72 Harv.L.Rev. 1482 (1959).
In. International Union U.A.W. v. Weatherhead Co. (N.D. Ohio 1962) 203 F.Supp. 612, in a case also dealing with contracting out, the agreement provided: ‘ The Impartial Arbitrator shall interpret and apply this Agreement but he shall not have authority to alter or modify the terms of this Agreement.” The court in comparing this provision with the one in Warrior Gulf observed: ‘By contrast, the contract in the instant litigation contained absolutely no provision limiting the scope of arbitration. ’' (At p. 615.)
See fn. 5, supra.
Association of Westinghouse Salaried Emp. v. Westinghouse Electric Corp. (3d Cir. 1960) 283 F.2d 93; International Union U.A.W. v. Cardwell Mfg. Co. (10th Cir. 1962) 304 F.2d 801; Note “Arbitrability” of Labor Disputes, 47 Va.L.Rev. 1182 (1961).