or acquire new job tasks when their own jobs are not threatened. . . ." Id., at 630–631 (emphasis added).1

We reaffirmed the National Woodwork analysis in ILA I, and noted that "a lawful work preservation agreement must pass two tests": the objective of the agreement must be preservation of work for members of the union rather than some secondary goal, and the "right of control" test of NLRB v. Pipefitters, 429 U. S. 507 (1977), must be satisfied. 447 U. S., at 504.16 We ruled, however, that the Board had

15 On this basis (the absence of a threat to union members' jobs) we distinguished boycotts of the type described in Allen Bradley Co. v. Electrical Workers, 325 U. S. 797 (1945), which the congressional sponsors of § 8(b)(4)(B) had sought to prohibit. In Allen Bradley, unionized employees of New York City electrical contractors had agreed with their local employers to boycott electrical equipment manufactured outside the city, in an effort "to secure benefits" for unionized employees of a different group of employers, the local electrical equipment manufacturers. 386 U. S., at 628-629; see 325 U. S., at 799-800. The union's agreement in Allen Bradley "was not in pursuance of any objective relating to pressuring their employers in the matter of their wages, hours, and working conditions; there was no work preservation or other primary objective" involved. 386 U. S., at 629 (emphasis in original). In this sense, the activity was purely acquisitive, indicating an unlawful secondary objective. Cf. Pipefitters, supra, at 528-530, n. 16 (condemning union attempts "not to preserve, but to aggrandize" its position); see Lesnick, Job Security and Secondary Boycotts: the Reach of NLRA §§ 8(b)(4) and 8(e), 113 U. Pa. L. Rev. 1000, 1017-1018 (1965).

16 Pipefitters also reaffirmed the basic premises of National Woodwork, noting that so long as the "right to control" test is satisfied, it will not normally violate § 8(b)(4)(B) to engage in activity against one's own employer "for the purpose of preserving work traditionally performed by union members even though in order to comply with the union's demand the employer would have to cease doing business with another employer." 429 U. S., at 510. See n. 12, supra. Pipefitters involved a refusal by union steamfitters to install equipment containing factory-installed piping specified by the general contractor, based on the unit's agreement with its employer, a subcontractor on the job, not to handle such equipment. Because the subcontractor did not have the right to control equipment specifications for the job, the union's refusal was found to violate § 8(b)(4)(B). 429 U. S., at 511-513, 528-531.

erred as an initial matter by defining the "work in dispute" as "off-pier" container loading and unloading. Id., at 506. Because technological innovation may significantly change the character of an industry, work preservation agreements negotiated to address such change "typically come into being when employees' traditional work is displaced." Id., at 505. Consequently, the place where work is to be done often lies at the heart of the controversy, and is seldom relevant to the definition of the work itself. See id., at 506-507." The Board's focus on the container work performed off-pier by nonlongshoremen was erroneous because it ignored the question whether "the parties have tailored their agreement to the objective of preserving the essence of the traditional work patterns," id., at 510, n. 24, and "foreclosed-by definition-any possibility that the longshoremen could negotiate an agreement to permit them to continue to play any part in the loading or unloading of containerized cargo." Id., at 508.

ILA I concluded, however, that collective-bargaining agreements designed to "accommodate change" while still preserving some type of work for union members may nevertheless be lawful primary agreements; the work preservation doctrine does not require that unions block progress by refusing to permit any use at all of new technology in order to avoid the prohibitions of §§ 8(b)(4)(B) and 8(e). Id., at 506. The inquiry is whether "the objective of the agreement was work preservation rather than the satisfaction of union goals elsewhere," id., at 510, and the analytical focus must be "on the work of the bargaining unit employees, not on the work of

17 Thus the definition of the work in dispute under the Rules on Containers used by the Board on remand was simply "the work of loading and unloading containers." 266 N. L. R. B., at 237. Although the Board also stated a precise description of the work claimed by the Rules-"the initial loading and unloading of cargo within 50 miles of a port into and out of containers owned or leased by shipping lines having a collective bargaining relationship with the ILA,” id., at 236-the less complex definition more accurately describes the work in controversy as opposed to the precise means used to secure it in the collective-bargaining agreement at issue.

other employees. . . doing the same or similar work." Id., at 507. "The effect of work preservation agreements on the employment opportunities of employees not represented by the union, no matter how severe, is of course irrelevant. .. so long as the union had no forbidden secondary purpose." Id., at 507, n. 22.18

Because the Board's analysis had proceeded from an erroneous premise, we remanded. We directed the Board to examine "how the contracting parties sought to preserve . . . work, to the extent possible, in the face of" containerization, and "to evaluate the relationship between traditional longshore work and the work which the Rules attempt to assign to ILA members." Id., at 509. If, on remand, the Rules were found to be a bona fide attempt to preserve longshore work, rather than an effort "tactically calculated to satisfy union objectives elsewhere,'" then the Rules would be valid. Id., at 511, quoting National Woodwork, 386 U. S., at 644. "[T]he question is not whether the Rules represent the most rational or efficient response to innovation, but whether they are a legally permissible effort to preserve jobs." 447 U. S., at 511.

B

We accept the Board's factual findings as supported by substantial evidence, Universal Camera Corp. v. NLRB, 340 U. S. 474 (1951), and are mindful of the rule that the Board's construction of the Act is due our deference. See, e. g., Beth Israel Hospital v. NLRB, 437 U. S. 483, 500-501 (1978); NLRB v. Erie Resistor Corp., 373 U. S. 221, 236 (1963). We are in agreement with the Board's basic statutory conclusions: §§ 8(b)(4)(B) and 8(e) prohibit secondary, but not

18 Cf. NLRB v. Retail Store Employees, 447 U. S. 607, 614 (1980) (“As long as secondary picketing only discourages consumption of a struck product, incidental injury to the neutral is a natural consequence of an effective primary boycott"); NLRB v. Operating Engineers, 400 U. S. 297, 303-304 (1971) ("primary activity is protected even though it may seriously affect neutral third parties" because "[s]ome disruption of business relationships is the necessary consequence of the purest form of primary activity").

primary, union activity, and bona fide work preservation agreements and their enforcement may constitute protected primary goals. Now that the Board has fully developed the factual record regarding the Rules, the only question presented is whether, as a matter of law, the Board applied the "work preservation" doctrine consistently with our prior

cases.

In our view, the Board committed two fundamental errors. First, by focusing on the effect that the Rules may have on "shortstopping" truckers and "traditional" warehousers, the Board contravened our direction that such extra-unit effects, "no matter how severe," are "irrelevant" to the analysis. 447 U. S., at 507, n. 22. “So long as the union had no forbidden secondary purpose" to disrupt the business relations of a neutral employer, ibid., such effects are "incidental to primary activity." Pipefitters, 429 U. S., at 526. Here the ALJ, Board, and Court of Appeals all have agreed that the Rules were motivated entirely by the longshoremen's understandable desire to preserve jobs against "the steadily dwindling volume" of cargo work at the pier. 734 F. 2d, at 978. Given this clear primary objective to preserve work in the face of a threat to jobs, extra-unit effects of a work preservation agreement alone provide an insufficient basis for concluding that the agreement has an unlawful secondary objective. Absent some additional showing of an attempt "to reach out to monopolize jobs," National Woodwork, supra, at 630, that is, proof of an attempt "not to preserve, but to aggrandize,” Pipefitters, supra, at 528-530, n. 16, such an agreement is lawful. 19

19 Amicus AFL-CIO suggests that any distinction between "work preservation" and "work acquisition" in this area distorts the primary/ secondary inquiry under §§ 8(b)(4)(B) and 8(e) and "virtually defies principled application in a situation in which technological advances have altered the nature of the work to be performed." Brief for American Federation of Labor and Congress of Industrial Organizations as Amicus Curiae 2-3. However, while we acknowledge that the dichotomy may be susceptible to wooden application, we are not prepared to abandon it. The "acquisition"

Second, we believe the Board misconstrued our cases in suggesting that "eliminated" work can never be the object of a work preservation agreement. Technological innovation will often by design eliminate some aspect of an industry's work. For example, in National Woodwork the agreement at issue strove to preserve carpentry work done by hand at the jobsite, even though new off-site machining techniques had eliminated the necessity for much of this work. Yet the jobs of carpenters were no less threatened, nor was their attempt to preserve them any less primary, than if the contractor had decided to subcontract the cutting and fitting of doors to nonunion workers. Cf. Fibreboard Corp. v. NLRB, 379 U. S. 203, 209 (1964). Similarly, containers have eliminated some of the work of loading and unloading cargo by hand for all participants in the industry-longshoremen, truckers, and warehousers alike.20 "Elimination" of work

concept in the work preservation area originated in National Woodwork, where we distinguished Allen Bradley, 325 U. S. 797 (1945), as involving "a boycott to reach out to monopolize jobs or acquire new job tasks when [union members'] own jobs are not threatened." 386 U. S., at 630-631 (emphasis added); see n. 15, supra. An agreement bargained for with the objective of work preservation in the face of a genuine job threat, however, is not "acquisitive" in the sense that concept was used in National Woodwork, even though it may have the incidental effect of displacing work that otherwise might be done elsewhere or not be done at all. See Pipefitters, 429 U. S., at 510, 526, 528--529, n. 16. Yet as the facts of Allen Bradley demonstrate, an agreement that reserves work for union members may also have an unlawful secondary objective. The preservation/acquisition dichotomy, when employed with the Allen Bradley distinction firmly in mind, can serve the useful purpose of aiding the inquiry regarding unlawful secondary objectives when an agreement attempts to secure work but "jobs are not threatened."

20 See, e. g., 266 N. L. R. B., at 255 ("With the introduction of containers, the off[-pier] [truck]drivers and their helpers. . . lost work themselves in connection with truckloading operations at pierside. In addition, dockworkers employed at trucking stations by motor carriers, after containerization, lost work in connection with FSL containers delivered directly over the road to warehouses, consignees, or interlining trucking stations . . .").