proscribed 'work acquisition' objective would attach." Ibid. He then found that, although the "skills utilized . . . are indistinct from those of deep sea longshoremen," cargo handling work done by shortstoppers and "traditional" warehousers is work "assumed for a different purpose" than longshore cargo handling and "preexisted" containerization. Id., at 256. He declared that the Rules therefore took on an impermissible secondary character when applied in those two contexts, and sustained unfair labor charges in three cases."

The Board adopted the ALJ's findings and conclusions, stating that "the ILA had an overall work preservation objective in negotiating the Rules," and that "the work of loading and unloading containers claimed by the Rules is functionally related to the traditional loading and unloading work of the longshoremen." Id., at 236, 237. The Board therefore held the Rules lawful as a general matter. It also agreed with the ALJ's partial invalidation "as applied," however, after modifying the ALJ's views in two respects.

First, the Board provided a definition of "the work in dispute," because the ALJ had not done so explicitly. Id., at 236. Second, the Board rejected the ALJ's "findings that an illegal work acquisition objective is revealed in the Rules,"

"Associated Transport ("shortstopping"); Terminal Corp. (warehousing); Beck Arabia (warehousing). 266 N. L. R. B., at 268, 269–270. Unfair labor charges also were sustained in Custom Brokers, but on a finding that the Rules had been employed in an unlawful attempt to organize two nonunion off-pier employers. 266 N. L. R. B., at 270-271. This finding was not challenged on appeal, 734 F. 2d, at 976, n. 7, and the Customs Brokers violations are not before us.

With respect to freight consolidators, the ALJ found that their container loading and unloading are performed "pursuant to a reallocation of work from the piers to off[-pier] facilities created virtually in its entirety by the development of containerization." 266 N. L. R. B., at 254. The ALJ consequently declared the Rules entirely valid as applied to preserve container work destined for consolidators. Ibid. The consolidators' charges were dismissed, as were the charges of one warehouser, Hill Creek Farms, found not to be engaged in "traditional" warehousing. Id., at 268-269.

because his analysis "appear[ed] to conflict" with the direction in ILA I to focus on the work of longshoremen, not offpier laborers. 266 N. L. R. B., at 236-237.

"By focusing on the economic character of the trucking and warehousing industry and on the work historically performed by trucking and warehousing employees, the [ALJ's] . . . findings give undue emphasis to the work historically performed by trucking and warehousing employees and to the fact that this work was not created by containerization." Ibid.

Nevertheless, the Board held the Rules unlawful "as applied to 'shortstopping' and 'traditional' warehousing practices." Id., at 236. The Board reasoned that some cargo loading and unloading work required to be performed by longshoremen under the Rules would unnecessarily duplicate the similar work done by "shortstopping" truckers and "traditional" warehousers. Because cargo in containers can now be moved directly to and from warehouses and trucking terminals without loading or unloading at the pier, the necessity for such longshore labor has been removed, while "traditional" warehousers and "shortstopping" truckers must still do some container loading and unloading at their facilities. Thus, the Board concluded, the loading and unloading work of the longshoremen "no longer exists as a step in the cargo handling process" and "essentially was eliminated" in these two contexts. Id., at 237. Because the Rules seek to preserve this "eliminated" work, the Board concluded that they have “an illegal work acquisition objective" as applied. Ibid. The Court of Appeals for the Fourth Circuit affirmed the Board's general validation of the Rules, concluding that the Board's crucial dual findings-that the shipping companies have the "right to control" container work, and that the Rules had a bona fide work preservation objective—were supported by substantial evidence. American Trucking Assns., Inc. v. NLRB, 734 F. 2d 966, 977-978 (1984). For

two reasons, however, the Court of Appeals refused to enforce the Board's decision that the Rules constitute unlawful secondary activity when applied to containers destined for "shortstopping" truckers and "traditional" warehousers.

First, in concluding that a partial objective of the Rules is "work acquisition," the Board had failed to make any factual finding that the Rules actually operate to deprive "shortstopping" truckers or "traditional" warehousers of any work. Id., at 979. Second, the Court of Appeals concluded that, as a matter of law, an agreement that preserves duplicative or technologically "eliminated" work simply does not constitute "work acquisition." National Woodwork had approved as lawful primary activity a collective-bargaining agreement whose objective was "protection of union members from a diminution of work flowing from changes in technology." 386 U. S., at 648 (Harlan, J., concurring). The ALJ and the Board both had found that the same work-preserving purpose underlies the Rules on Containers. The Rules do not "in any way prevent the identical off-pier work," and although such work may be economically inefficient, "it is not our function as a court of review to weigh the economic cost of the Rules." 734 F. 2d, at 979. The Court of Appeals therefore concluded that "the Rules are lawful in their entirety and may be enforced." Id., at 980.

Although a number of the charging parties sought review of the Fourth Circuit's decision, we granted only the Board's petition for certiorari, 469 U. S. 1188 (1985), thereby limiting our inquiry to the alleged unlawfulness of the Rules with regard to "shortstopping" truckers and "traditional" warehousers.

II
A

We have labored in the past to determine Congress' will as expressed in §§ 8(b)(4)(B) and 8(e)-this case requires no new development. In light of the Board's factual findings,

we believe the Court of Appeals' conclusion that the Rules do not violate these provisions, flows as a matter of course from National Woodwork and ILA I.12

In National Woodwork, after reviewing in detail the relevant legislative and judicial history, we concluded that "Congress meant that both § 8(e) and § 8(b)(4)(B) reach only secondary pressures." 386 U. S., at 638; accord, Houston Contractors Assn. v. NLRB, 386 U. S. 664, 668 (1967).13 In this regard, the prohibitory scope of § 8(e) was found to be no broader than that of § 8(b)(4)(B). 386 U. S., at 635, 638. The purpose of § 8(e) had been to close a "loophole" in the labor laws that allowed unions to employ "hot cargo" agree

12 The dissent apparently agrees with this assessment of our precedents, as its criticisms are directed largely at the rationales of National Woodwork and ILA I. See post, at 88-90. The rationale of our third major precedent in this area, NLRB v. Pipefitters, 429 U. S. 507 (1977), is not directly implicated in this case. Pipefitters held that activity taken to enforce a valid work preservation agreement will violate § 8(b)(4)(B) if the primary employer "does not have control over the assignment of the work sought by the union." Id., at 510-511. In this case, the ALJ, Board, and Court of Appeals have unanimously concluded that the longshoremen's employers, marine shipping companies, have the "right to control" container loading and unloading work by virtue of their ownership or leasing control of the containers. See 734 F. 2d, at 978; 266 N. L. R. B., at 234, 260–267. Thus the Pipefitters test is satisfied here.

"Our review in National Woodwork extended back to § 20 of the Clayton Act of 1914, 38 Stat. 738, and the decisions in Duplex Printing Press Co. v. Deering, 254 U. S. 443 (1921), and Bedford Cut Stone Co. v. Stone Cutters, 274 U. S. 37 (1927), which had held that § 20 immunized from the antitrust laws only those union activities "directed against an employer by his own employees." 386 U. S., at 621. We determined that Congress' intent in enacting the Taft-Hartley Act in 1947, 61 Stat. 136, and the Landrum-Griffin Amendments in 1959, 73 Stat. 519, which contained § 8(b) (4)(B) and § 8(e), respectively, had been to maintain this early distinction between primary and secondary union activity. 386 U. S., at 620-638. Today's dissent cites no new legislative history or other evidence to the contrary. See post, at 88; see also post, at 90-91 (§ 8(e) cannot be read literally, "because many labor-management ‘agreements' will entail some secondary effects").

ments to pressure neutral employers not to handle nonunion goods. Id., at 634-637; see Carpenters v. NLRB, 357 U. S. 93 (1958) (Sand Door). However, we concluded, "Congress in enacting §8(e) had no thought of prohibiting agreements directed to work preservation." 386 U. S., at 640.14 Such agreements "are not used as a sword" to achieve secondary objectives, but as "a shield carried solely to preserve the members' jobs." Id., at 630. Because the labor laws do not prohibit bona fide primary activity, we stated that the central inquiry for evaluating claims of work preservation is

"whether, under all the surrounding circumstances, the Union's objective was preservation of work for [the primary employer's] employees, or whether the agreements and boycott were tactically calculated to satisfy union objectives elsewhere. . . . The touchstone is whether the agreement or its maintenance is addressed to the labor relations of the contracting employer vis à vis his own employees." Id., at 644-645.

We expressly noted that a different case might be presented if a union engaged in activity "to reach out to monopolize jobs

"Specifically at issue in National Woodwork was an agreement between a general contractor and its carpenters' union that union workers would not handle prefabricated doors. Carpenters had traditionally cut and installed blank doors at the jobsite, and the will-not-handle clause had been bargained for with the objective of preserving that work in the face of more efficient off-site technology. The record in National Woodwork indicated that it took a machine eight minutes to finish a door with on-site installation requiring only a few more minutes, while a carpenter at the jobsite would take over an hour to perform the same work. Brief for Petitioners in National Woodwork Manufacturers Assn. v. NLRB, O. T. 1966, No. 110, p. 5, n. 4. Unfair labor charges were filed by suppliers of the prefabricated doors, who claimed that the will-not-handle agreement was unlawfully secondary because it caused the contractor to cancel his business with the suppliers. We upheld the agreement and its enforcement, however, as lawful primary activity engaged in to preserve the carpenters' work. 386 U. S., at 645–646.