dissenting:
Appellant Winter, a truck driver engaged in the delivery of concrete in the Washington, D. C. metropolitan area, is an employee of Maloney Concrete Company (hereinafter “Maloney”) and a member of Local No. 639 of the Teamsters International Union. Maloney has several plants from which mixed concrete is delivered, and each driver is assigned to a particular plant. The collective bargaining agreement between Maloney and the union has a seniority provision which reads as follows:
When ability, merit, and physical fitness are equal, employees with the greatest seniority will be given preference in advancement to higher-rated jobs, except promotions to positions excluded from the coverage of this agreement. Increases or decreases of working forces shall also be on the same basis.
(App. 9).
Winter’s lawsuit alleges that Maloney breached this provision by according him only “plant wide” rather than “company wide” seniority, and that the union breached its duty of fair representation in its handling of two grievances that he filed in 1971 and 1974 protesting the company’s failure to comply in this respect with the collective bargaining agreement.
On motion by the union for summary judgment, the district court dismissed the complaint as to the union on the ground that Winter had failed
to exhaust the internal remedies available to all union members under the constitution, such exhaustion being a prerequisite to commencement of any civil action, Imel v. Zohn Manufacturing Co., 481 F.2d 181 (10th Cir. 1973), cert. denied, 415 U.S. 915, 94 S.Ct. 1411, 39 L.Ed.2d 469 (1974); compare Vaca v. Sipes, 386 U.S. 171, 87 S.Ct. 903, 17 L.Ed.2d 842 (1967).
The district court also granted Maloney’s motion for summary judgment for the following stated reasons:
In view of the Court’s holding that plaintiff has failed to exhaust his internal union remedies, the Court is now compelled to dismiss plaintiff’s complaint as to Maloney for similar reasons. Vaca v. Sipes, supra; Republic Steel v. Maddox, 379 U.S. 650, 85 S.Ct. 614, 13 L.Ed.2d 580 *153(1965); Scott v. Anchor Motor Freight, Inc., 496 F.2d 276 (6th Cir.), cert. denied, 419 U.S. 868, 95 S.Ct. 126, 42 L.Ed.2d 107 (1974); Hubicki v. ACF Industries, Inc., 484 F.2d 519 (3d Cir. 1973).
(App. 90).
I agree with the majority opinion, on the facts of this case, that the defense of failure to exhaust union remedies is not available to the employer, Maloney1; but I disagree with its conclusion that it was proper for the district court to grant summary judgment on the alternative ground that “there was no breach of the collective bargaining contract by Maloney Concrete Company.” In my opinion whether there was a breach of the collective bargaining agreement presents a genuine issue of material fact that must be resolved by testimony at trial. Fed.R.Civ.P. 56(c); Poller v. Columbia Broadcasting System, Inc., 368 U.S. 464, 82 S.Ct. 486, 7 L.Ed.2d 458 (1962); Ecology Center of Louisiana, Inc. v. Coleman, 515 F.2d 860 (5th Cir. 1975); Underwater Storage, Inc. v. United States Rubber Co., 125 U.S.App.D.C. 297, 371 F.2d 950 (1966), cert. denied, 386 U.S. 911, 87 S.Ct. 859, 17 L.Ed.2d 784 (1967), on remand 314 F.Supp. 546 (D.D.C.1970).
The affidavits filed by the appellees assert that it was a long-standing practice at Maloney and in the local industry in general to afford work opportunity to employees, under contracts such as the one involved here, on the basis of plant-wide rather than company-wide seniority (App. 25-42). Winter, however, while not disputing that plant-wide seniority may be the norm in the industry at large, insists that the specific terms of the collective bargaining agreement between Local 639 and Maloney are at variance with any such allegedly “established practice” and require company-wide seniority. The bargaining agreement does not explicitly refer to either “plant-wide” or “company-wide” seniority. The relevant provision, set forth above, is from the agreement made with the Maloney Company as a whole, not with its individual plants. In the absence of some specific provision or persuasive evidence to the contrary, an *154agreement with a company looks to company-wide, not merely plant-wide, obligations. Maloney introduces a number of affidavits stating that the practice both at Maloney itself and in the industry at large was to have only plant-wide seniority. Not only, however, is evidence of general practice insufficient to override the express terms of a contract, but also, where a contract’s meaning is unclear, summary judgment is inappropriate.
Although summary judgment is possible on questions of contractual interpretation, see, e. g., Parish v. Howard, 459 F.2d 616 (8th Cir. 1972); Green v. Valve Corp. of America, 428 F.2d 342 (7th Cir. 1970); Universal Fiberglass Corp. v. United States, 400 F.2d 926 (8th Cir. 1968), where the contract is ambiguous, such disposition is prohibited, see, e. g., Cram v. Sun Insurance Office, Ltd., 375 F.2d 670 (4th Cir. 1967); Cinocca v. Baxter Laboratories, Inc., 400 F.Supp. 527 (E.D.Okl.1975).
Moreover, the burden is on the party moving for summary judgment to prove that there are no material issues of fact (such as ambiguous contract terms), see, e. g., Adickes v. Kress & Co., 398 U.S. 144, 90 S.Ct. 1598, 26 L.Ed.2d 142 (1970); In re Coordinated Pretrial Proceedings in Antibiotic Antitrust Action, 538 F.2d 180 (8th Cir. 1976), cert. denied, 429 U.S. 1040, 97 S.Ct. 738, 50 L.Ed.2d 751 (1977); Evers v. Buxbaum, 102 U.S.App.D.C. 334, 253 F.2d 356 (1958); and disputed issues of fact may not be tried by affidavit, Sartor v. Arkansas Malt Gas Corp., 321 U.S. 620, 64 S.Ct. 724, 88 L.Ed. 967 (1944); Redman v. Warrener, 516 F.2d 766 (1st Cir. 1975); Gutor International AG v. Raymond Packer Co., Inc., 493 F.2d 938 (1st Cir. 1974); Hollander v. Pan Am World Airways, Inc., 382 F.Supp. 96 (D.Md.1973); 6 Moore’s Federal Practice 1 56.11[l.-2] (2d ed. 1977).
In this case, it cannot be successfully maintained that the terms of this collective bargaining agreement are clear on their face, cf. Dworman v. Mayor and Board of Aldermen, Governing Body of Town of Morristown, 370 F.Supp. 1056 (D.N.J.1974); La Salle Co. v. Kane, 8 F.R.D. 625 (E.D.N. Y.1949), and Maloney has not carried its burden of persuasion that they are in fact unambiguous. The court, then, is presented with a genuine issue of material fact that can be resolved only at trial, to wit, whether:
The alleged “established practice in the concrete industry in the Washington metropolitan area that work opportunity is offered employees in the order of seniority on a plant . . . basis . . . ” as applied by defendants in this case, violates the seniority provisions of the agreement and discriminatorily violates plaintiff’s rights.
(App. 52).
The question of contract interpretation is sufficient to preclude summary judgment in favor of Maloney. In addition, the other issues of material fact presented by Winter’s claim that the union breached its duty of fair representation by failing to process his grievances and persisting for political reasons in its refusal to enforce his seniority rights (App. 9-10, 49) would require a similar conclusion as regards Winter’s case against Local 639.
On the controverted issue as to whether the union discriminatorily refused to enforce his contractual seniority rights, Winter swears that his allegations of political motivation are made on “personal knowledge of the facts” (App. 11), while the Local contends that it processed plaintiff’s grievances and disposed of them on the merits.
We need not reach the question of which of the parties’ version of the facts is more credible. Any such determination is clearly to be made by the fact-finder in an actual trial. This court cannot uphold the summary disposition of genuine issues of material fact. In a summary judgment proceeding a court cannot try issues of fact, but only determine whether there are such issues to be tried, see, e. g., Heyman v. Commerce and Industry Insurance Co., 524 F.2d 1317, 1319-1320 (2d Cir. 1975); and genuine questions of fact must be resolved at trial, not merely by affidavits such as were before the district court in this case, see, e. g., Judge v. City of Buffalo, 524 F.2d 1321 (2d *155Cir. 1975); Redman v. Warrener, 516 F.2d 766 (1st Cir. 1975); Aeronca, Inc. v. Style-Crafters, Inc., 499 F.2d 1367 (4th Cir. 1974), later appeal, 546 F.2d 1094 (1976); Aulds v. Foster, 484 F.2d 945 (5th Cir. 1973); Jackson v. Griffith, 480 F.2d 261 (10th Cir. 1973).
The union contends that Winter “made no attempt to invoke his available internal union remedies” (App. 13), and he in turn rejoins that any attempt to do so would have been futile (App. 9-10, 49). The issue is thus raised as to whether or not the political antagonism of the union to Winter was sufficiently intense that it would be unreasonable to suppose that his grievances would be fairly advanced by the union. One need not exhaust union remedies if they are shown likely to be futile. Cf. Verville v. International Ass’n of Machinists & Aerospace Workers, 520 F.2d 615, 620 (6th Cir. 1975); Semanick v. UMW District 5, 466 F.2d 144,151 (3d Cir. 1972); Farowitz v. Associated Musicians of Greater New York, 330 F.2d 999 (2d Cir. 1964).
The critical evidence on this point relates to whether the business agent, Marcey, who handled — or mishandled as the case may be — both of Winter’s grievances knew when he did so of Winter’s activities in support of Marcey’s opponents within the union. Mar-cey claims that he had “no knowledge other than the allegations in the complaint that Winter was engaged in any internal union political activity” (App. 30). His position, however, is controverted by the affidavit of another member of Local 639 who states that he recollects “Mr. Marcey was present at most of [the] meetings, and in a few cases I believe he chaired the meetings in the absence of President DeBrouse” when “Mr. Winter was critical of seniority practices and use of temporary employees in the construction industry, and had some argument on these or related matters with President DeBrouse during meetings” (App. 56). When the affidavits reveal such a conflict over facts that substantially affect the position of a party on a material matter, summary judgment is not to be granted, see, e. g., Jackson v. Griffith, supra, 480 F.2d at 267; Machinery Center, Inc. v. Anchor National Life Insurance Co., 434 F.2d 1, 6 (10th Cir. 1970). The materiality of this evidence does not lie in a “mere showing of . awareness” of Winter’s political activity but in Marcey predicating his denial of hostility to Winter on the claim that he never knew of his political activity within the union. This evidence is thus material on the issue of hostility.
The majority opinion gives far too short shrift to the importance of the fact that the union officials knew of appellant’s agitation and activities against their leadership. Of course, this fact alone is not conclusive, but it certainly is probative. In my view, appellant has suggested sufficient other evidence of the union’s hostility that, taken together with his expressed dissatisfaction with the union, he should have his day in court. Knowledge of a union member’s protest activities may not prove union bias against him, but — human nature being what it is — it must lead the court closely to scrutinize such evidence for the possibility of such hostility. Applying such scrutiny here, summary judgment is unjustifiable.
At trial, the question of whether Marcey and the union did or did not process Winter’s grievances in accordance with their statutory duty must be resolved. At present — despite the broad discretion traditionally accorded to unions in the exercise of their obligation of fair representation, see Ford Motor Co. v. Huffman, 345 U.S. 330, 338, 73 S.Ct. 681, 97 L.Ed. 1048 (1953); Blumrosen, The Workers and Three Phases of Unionism: Administrative and Judicial Control of the Worker-Union Relationship, 61 Mich.L.Rev. 1435, 1469-1472 (1963)— genuine issues exist as to whether these complaints were processed at all. Assuming that they were, the issue remains as to whether they were fairly evaluated, whether Winter was adequately advised, etc. Similarly, the question of the construction of the seniority provision of the collective bargaining agreement must be resolved in order to decide the suits against Maloney. When such issues remain controverted and unresolved, the only acceptable procedure is to deny summary judgment, go beyond the affidavits, and hold a trial on the merits. *156It is thus my conclusion that the summary judgments granted to Maloney and Local 639 should be vacated and the cases remanded for further proceedings. To this end, I respectfully dissent.
. Although I agree with the majority’s holding that Maloney cannot rely on Winter’s failure to exhaust his internal remedies, I adopt a slightly different rationale for doing so, based in part on the analysis in Brookins v. Chrysler Corporation, Dodge Main Division, 381 F.Supp. 563 (E.D.Mich.1974). In Brookins, the court gave a cogent summary of the dilemma that the ruling in Vaca v. Sipes, 386 U.S. 171, 87 S.Ct. 903, 17 L.Ed.2d 842 (1967) has provoked:
The answer [to whether an employer may rely on an employee’s failure to exhaust his union remedies] seems to turn on whether the union’s successful exhaustion defense goes to the merits of the claimed unfair representation or merely to the ripeness of the controversy or plaintiffs capacity to sue. If the former — i. e., if a failure to exhaust internal remedies means that the duty of fair representation has not yet been breached— then plaintiff clearly cannot prove the contrary and the employer may properly rely on the employee’s failure to exhaust contractual remedies, for he has through the judgment of dismissal as to the union lost his only legally valid excuse for failing to exhaust. In that sense the employer does indeed get a “free ride” on the union’s defense. However, if the union’s dismissal for failure to exhaust internal remedies recognizes that a breach of the duty of fair representation may have occurred, and holds only that a judicial remedy for that breach is not presently available, then it seems that the plaintiff would be in a position to prove the existence of the breach despite the fact that he cannot at present maintain an action thereon. The wrong could still exist, and would be subject to proof; only the timing of the remedy would be affected by the union’s dismissal from the case.
381 F.Supp. at 567-68.
Thus, by the same token that an exhaustion of internal union remedies is not an absolute requirement for suit against the union itself, it cannot be an absolute prerequisite to suit against the employer. In the instant case, it is my opinion that there is enough suspicion of union-employee hostility that appellant should not be forced to exhaust his internal union remedies before suing the union for breach of its duty of fair representation. Accordingly, the exhaustion requirement is clearly not “substantive” in the sense the Brookins opinion suggests, and thus the employer cannot rely upon it as a defense. Should Winter’s claims of official hostility prove unsubstantiated, upon dismissal of his suit against the union his suit against Maloney must also be dismissed, Vaca v. Sipes, supra; but he should not as a matter of law be foreclosed from having a hearing on his grievances because he has not exhausted his union grievances.