In the case of National Labor Relations Board v. Denver Building & Construction Trades Council et al., 1950, the U.S. Supreme Court ruled in favor of the National Labor Relations Board (NLRB). The dispute involved a construction project where union workers refused to work alongside non-union workers, leading to a halt in operations. The NLRB argued that this constituted an unfair labor practice under Section 8(b)(4)(A) of the Taft-Hartley Act which prohibits unions from coercing employers into discriminatory practices against non-union employees. The court agreed with NLRB's interpretation and held that such secondary boycotts were indeed illegal as they disrupted commerce and violated employer neutrality rights by forcing them to participate in labor disputes not their own.

In the dissenting opinion for the case of NATIONAL LABOR RELATIONS BOARD v. DENVER BUILDING & CONSTRUCTION TRADES COUNCIL ET AL., Justice Black argued that the majority misinterpreted and overstepped their bounds in applying federal labor laws to this dispute. He contended that Congress did not intend for these laws to be used as a means of settling every labor dispute, but rather only those which had a direct impact on commerce or led to industrial strife and unrest. In his view, there was no evidence presented in this case showing such an effect on commerce or potential for unrest. Therefore, he believed it was inappropriate for the court to intervene in what should have been handled as a local matter between contractors and unions under state law.