MR. JUSTICE BRENNAN delivered the opinion of the Court.

Under the Landrum-Griffin Act amendments enacted in 1959, § 8 (b)(4)(A) of the National Labor Relations Act became $8 (h)(4)(B) and § 8 (e) was added. The questions here are whether, in the circumstances of this case, the Metropolitan District Council of Philadelphia and Vicinity of the United Brotherhood of Carpenters and Joiners of America, AFL-CIO (hereafter the Union), committed the unfair labor practices prohibited by §§ 8 (e) and 8 (b)(4)(B).'

Frouge Corporation, a Bridgeport. Connecticut concern, was the general contractor on a housing project in Philadelphia. Frouge had a collective bargaining agreement with the Carpenters' International Union under which Frouge agreed to be bound by the rules and regulations agreed upon by local unions with contractors in areas in which Frouge had jobs. Frouge was therefore subject to the provision of a collective bargaining agreement between the Union and an organization of Philadelphia contractors, the General Building Contractors Association, Inc. A sentence in a provision of that agreement entitled Rule 17 provides that "... no member of the District Council will handle... any doors... which have been fitted prior to being furnished on the job...."

'The text of these sections appears in the Appendix. The full text of Rule 17 is as follows:

"No employer shall work on any job on which cabinet work, fixtures, nill work, sash doors, trim or other detailed millwork is used unless the same is Union-made and bears the Union Label of the United Brotherhood of Carpenters and Joiners of America. No member of this District Council will landle material coming from a mill where cutting out and fitting has been done for butts, locks, letter plates, or hardware of any description, nor any doors or tran

Frouge's Philadelphia project called for 3.600 doors. Customarily, before the doors could be hung on such projects, "blank" or "blind" doors would be mortised for the knob, routed for the hinges, and beveled to make them fit between jambs. These are tasks traditionally performed in the Philadelphia area by the carpenters employed on the jobsite. However, preent and prefitted doors ready to hang may be purchased from door manufacturers. Although Frouge's contract and job specifications did not call for premachined doors, and “blank” or "blind" doors could have been ordered. Frouge contracted for the purchase of premachined doors from a Pennsylvania door manufacturer which is a member of the National Woodwork Manufacturers Association. petitioner in No. 110 and respondent in No. 111. The Union ordered its carpenter members not to hang the doors when they arrived at the jobsite. Frouge thereupon withdrew the prefabricated doors and substituted "blank" doors which were fitted and cut by his carpenters on the job-site.

The National Woodwork Manufacturers Association and another filed charges with the National Labor Relations Board against the Union alleging that by including the "will not handle" sentence of Rule 17 in the collective bargaining agreement the Union committed the unfair labor practice under $8 (e) of entering into an "agreement... whereby. [the]... employer... agrees to cease or refrain from handling.. any of the products of any other employer . . . ." and alleging further that in enforcing the sentence against Frouge, the Union committed the unfair labor practice under $8 (b)(4)(B) of "forcing or requiring any person to cease using. the products of any other... manufacturer...." The National Labor Relations Board dismissed the charges. 149 N. L. R. B. 646. The Board adopted the findings

soms which have been fitted prior to being furnished on job, includs ing base, chair, rail, pieture moulding, which has been previously fitted. This section to exempt partition work furnished in sections," The National Labor Relations Board determined that the first sens tence violated § 8 (c), 149 N. L. R. B. 646, 655-656, and the Union did not seek judicial review of that determination,

(b)(4)(B)

a There were also charges of violation of §§ 8 (e) and arising from the enforcement of the Rule 17 provision against three other contractors whose contracts with the owners of the construc tion projects involved specified that the contractors should furnish and install preeut and prefinished doors, The Union refused to permit its members to hang these doors. The Board held that this refusal violated §5 (b)(4)(B). The Board reasoned that, since these contractors (in contrast to Frouge) did not have "control" over the work that the Union sought to preserve for its members, the Union's objective was secondary-to compel the project owners to stop specifying present doors in their contracts with the employer

of the Trial Examiner that the "will not handle" sentence in Rule 17 was language used by the parties to protect and preserve cutting out and fitting as unit work to be performed by the jobsite carpenters. The Board also adopted the holding of the Trial Examiner that both the sentence of Rule 17 itself and its maintenance against Frouge were therefore "primary" activity outside the prohibitions of $88 (e) and 8 (b)(4)(B). The following statement of the Trial Examiner was adopted by the Board:

"I am convinced and find that the tasks of entting out and fitting millwork, including doors, has. at least customarily, been performed by the carpenters employed on the jobsite. Certainly, this provision of Rule 17 is not concerned with the nature of the employer with whom the contractor does business nor with the employment conditions of other employers or employees. The provision guards against encroachments on the cutting out and fitting work of the contract unit employees who have performed that work in the past. Its purpose is plainly to regulate the relations between the general contractor and his own employees and to protect a legitimate economic interest of the employees by preserving their unit work. Merely because it incidentally also affects other parties is no basis for invalidating this provision.

"I find that... [the provision] is a lawful work protection or work preservation provision and that Respondents have not violated Section 8 (e) of the Act by entering into agreements containing this provision and by thereafter maintaining and enforcing this provision." 149 N. L. R. B., at 657.

The Court of Appeals for the Seventh Circuit reversed the Board in this respect. 354 F. 2d 594, 599. The court held that the "will not handle" agreement violated $8 (e) without regard to any "primary" or "secondary" objective, and remanded to the Board with instructions to enter an order accordingly. In the court's view, the sentence was designed to effect a product boycott like the one condemned in Allen Bradley Co. v. Local Union No. 3, 325 U. S. 797, and Congress meant, in enacting §8 (e) and §8 (b)(4) (B), to prohibit such agreements and conduct forcing employers to enter into them.

The Court of Appeals sustained, however, the dismissal of the $8 (b)(4)(13) charge. The court agreed with

contractors. 149 N. L. R. B., at 658. The Union petitioned the Court of Appeals to set aside the remedial order issued by the Board on this finding, but the court sustained the Board. 354 F. 24, at 597 The Union did not seek review of the question here. Not before us, therefore, is the issue argued by the AFL-CIO in its brief amicus curide, namely, whether the Board's "right-to-control doctrine-that employees can never strike against their own employer about a matter over which he lacks the legal power to grant their demand" is an incorrect rule of law inconsistent with the Court's decision in Labor Board v. Insurance Agents' International Union 361 U. S. 477, 497-498.

the Board that the Union's conduct as to Frouge involved only a primary dispute with him and held that the conduct was therefore not prohibited by that section but expressly protected by the proviso "that nothing contained in this clause (B) shall be construed to make unlawful, where not otherwise unlawful, any primary strike or primary picketing . . . ." Id., at 597.

We granted certiorari on the petition of the Woodwork Manufacturers Association in No. 110 and on the petition of the Board in No. 111. 384 U. S. 968. We affirm in No. 110 and reverse in No. 111.

1.

Even on the doubtful premise that the words of $8 (e) unambiguously embrace the sentence of Rule 17, this does not end inquiry into Congress' purpose in enacting the section. It is a "familiar rule, that a thing may In within the letter of the statute and yet not within the statute, because not within its spirit, nor within the inten tion of its makers." Holy Trinity Church v. United States, 143 U. S. 457, 459. That principle has particular appbration in the construction of labor legislation which is "to a marked degree, the result of conflict and compromise between strong contending forces and deeply held views on the role of organized labor in the free economic life of the Nation and the appropriate balance to be struck between the uncontrolled power of management and labor to further their respective interests." Local 1976, United Brotherhood of Carpenters v. Labor Board, 357 U. S. 93, 99-100. Sec. c. g., Labor Board v. Fruit & Vegetable Packers, 377 U, S. 58; Labor Board v. Servette, Inc., 377 V. S. 46; Labor Board v. Drivers Local Union, 362 U. S. 274; Mastro Plastics Corp. v. Labor Board, 350) U. S. 270; Labor Bourd v. Lion Oil Co., 352 U. S. 22; Labor Board v. International Rice Milling Co., 341 U.S. 665; Local 761, Electrical Workers v. Labor Board, 366 U. S. 667.

Strongly held opposing views have invariably marked controversy over labor's use of the boycott to further its aims by involving an employer in disputes not his own. But congressional action to deal with such conduct has stopped short of proscribing identical activity having the object of pressuring the employer for agreements regulating relations between him and his own employees. That Congress meant §§ 8 (e) and 8(b)(4)(B) to prohibit only "secondary" objectives clearly appears from an examination of the history of congressional action on the subject; we may, by such an examination, "recon

The statutory language of §8 (e) is far from unambiguous It prohibits agreements to erase from handling. any of the products of any other employer Emphasis supplied. | Since both the product and its source are mentioned, the provisióti might be read not to prohibit an agreement relating solely to the nature of the product itself, such as a work preservation agrevineri, but only to prohibit one arising from an objection to the other employers or a definable group of employers who are the souter of the product, for example, their nonumaon statis

stitute the gainut of values current at the time when the words were uttered." "

The history begins with judicial application of the Sherman Act to labor activities. Federal court injunc tious freely issued against all manner of strikes and boycotts under rulings that condemned virtually every collective activity of labor as an unlawful restraint of trade. The first congressional response to vehement labor protests came with $ 20 of the Clayton Act in 1914. That section purported drastically to limit the injunction power of federal courts in controversies "involving, or growing out of, a dispute concerning terms or conditions of employment." In terms, it prohibited restraining any person from "ceasing to perform any work or labor" or "from ceasing to patronize or to employ any party to such dispute, or from recommending, advising, or persuading others by peaceful and lawful means so to do." 38 Stat. 730, 738. Labor hailed the law as a charter immunizing its activities from the antitrust laws. This expectation was disappointed when Duplex Printing Press Co. v. Deering, 254 U. S. 443, and Bedford Cut Stone Co. v. Journeymen Stone Cutters' Assn., 274 U. S. 37, held that $20 immunized only trade union activities directed against an employer by his own employees. In Duplex, the union carried on an elaborate scheme to coerce and restrain neutral customers of the complainant manufacturer from dealing with it, with the object of using these customers as an economic lever to bring the nonunion inanufacturer to terms. The Court there stated:

"The substance of the matters here complained of is an interference with complainant's interstate trade, intended to have coercive effect upon complainant, and produced by what is commonly known as a 'secondary boycott,' that is, a combination not merely to refrain from dealing with complainant, or to advise or by peaceful means persuade complainant's customers to refrain ('primary boycott'), but to exercise coercive pressure upon such customers, actual or prospective, in order to cause them to withhold or withdraw patronage from complainant through fear of loss or damage to themselves

*Letter of Judge Learned Hand, quoted in Lesnick, The Gravamen of the Secondary Boycott, 62 Col. L. Rev. 1363, 133-1304, n. 155 (1962). See II Sutherland, Statutory Construction 321 (Horack ed. 1940): "Before the true meaning of the statute can be determined consideration must be given to the problem in society to which the legislature addressed itself, prior legislative consideration of the problem, the legislative history of the statute under litigation, and to the operation and administration of the statute prior to litigation."

See Loewe v. Lmelor, 208 U. 8, 274, and 235 U. 8. 522 (Danbury Hatters Case). The history of this development under the Sherman Act is traced in Dupler Printing Press Co. v. Deering, 254 U, 8.443; Allen Bradley Co. v. Local 3, Electrical Workers, 325 U. 8. 797, 800-803. See generally, Berman, Labor and the Sherman Act (1930). Collective activity was also being restrained through the doetrine of "malicious combination." See Duplex Printing Press Co. v. Deering, supra, at 484-485 (Brandeis, J., dissenting); see generally Laidler, Boycotts and the Labor Struggle, 189-194 (1914).

should they deal with it." Duplex Printing Press Co. v. Deering, supra, at 466.

Thus "primary" but not "secondary" pressures were excepted from the antitrust laws. Truar v. Corrigan, 257 U. S. 312, 330, defined "secondary boycott" as one "where many combine to injure one in his business by coercing third persons against their will to cease patronizing him by threats of similar injury. . . . The question in such cases is whether the moral coercion exercised over a stranger to the original controversy by steps in themselves legal becomes a legal wrong." See 1 Teller. Labor Disputes & Collective Bargaining § 145 (1940).' Commentators of the day, while noting the ambiguity which lurked in the definition, discerned its core concept: union pressure directed at a neutral employer the object of which was to induce or coerce him to cease doing business with an employer with whom the union was engaged in a labor dispute."

In 1932 Congress enacted the Norris-LaGuardia Act and tipped the scales the other way. Its provisions "established that the allowable area of union activity was not to be restricted, as it had been in the Duplex case, to an immediate employer-employee relation." United States v. Hutcheson, 312 U. S. 219, 231." Congress abolished, for purposes of labor immunity, the distinction between primary activity between the "immediate disputants" and secondary activity in which the employer disputants and the members of the union do not stand "in the proximate relation of employer and employee...." H. R. Rep. No. 660, 72d Cong., 1 Sess., 8 (1932). Thus, in Hutcheson, supra, the Court held that the NorrisLaGuardia Act immunized a jurisdictional strike trapping a neutral employer in the middle of an "internecine struggle between two unions seeking the favor of the same employer," supra, at 232, Commentators of the post-Norris-LaGuardia era, as those before, while continuing to deplore the chameleon-like qualities of the term "secondary boycott." agreed upon its central aspect:

Painters District Council v. United States, 284 U. S. 582, which summarily affirmed 44 F. 2d 58, also involved secondary activity within the nibrie of Duplex: the union, whose members' primary employers were painting contractors, sought to "compel manufacturers to bring their products into the state unfinished...." +4 F. 24, at 59. (Emphasis supplied.)

See Laidler, op. cit. supra, note 6, at 64; Clark, The Law of the Employment of Labor 289-290 (1911); Oakes, Organized Labor and Industrial Conflicts § 408 (1927); Frankfurter & Greene, The Labor Injunction 43 (1930).

Section 13 (c) of the Norris-LaGuardia Act provided that the term labor dispute and thus the scope of immunity "includes any controversy concerning terms or conditions of employment, or concerning the association or representation of persons in negotiating, fixing, maintaining, changing, or seeking to arrange terms or condi tions of employment, regardless of whether or not the disputants stand in the prozimate relation of employer and employee." 47 Stat. 70, 73. (Emphasis supplied.)