In the case of Mastro Plastics Corp. et al. v. National Labor Relations Board, 1955, the U.S Supreme Court upheld a decision by the National Labor Relations Board (NLRB) that found Mastro Plastics Corporation guilty of unfair labor practices under Section 8(a)(1) and (3) of the National Labor Relations Act for discharging employees due to their union activities and refusing to reinstate them after a strike had ended. The court ruled that an employer cannot discharge or refuse reinstatement to striking workers because they engaged in acts of violence during a strike unless those acts were so violent as to cause "a general loss in confidence" among other employees or customers about safety at work or business continuity respectively.

In the dissenting opinion for Mastro Plastics Corp. v. National Labor Relations Board, Justice Reed argued that the majority's decision to allow union members to picket an employer during a labor dispute was inconsistent with previous court rulings and federal law. He contended that such actions could lead to coercion or intimidation of employees who did not wish to join the strike, infringing on their rights under Section 7 of the National Labor Relations Act (NLRA). Furthermore, he believed this ruling would encourage disruptive behavior and potentially violent confrontations between striking workers and those choosing not to participate in strikes. In his view, allowing picketing in these circumstances undermined peaceful negotiation processes established by NLRA provisions designed specifically for resolving labor disputes without resorting to economic warfare tactics like strikes or lockouts.