In the case of National Labor Relations Board v. Curtin Matheson Scientific, Inc., 1989, the Supreme Court ruled in favor of Curtin Matheson Scientific. The dispute arose when the company hired replacement workers during a labor strike and refused to reinstate striking employees after they offered unconditionally to return to work. The National Labor Relations Board (NLRB) argued that this was an unfair labor practice as it presumed that these replacements were anti-union and thus their hiring was discriminatory against union members. However, the Supreme Court disagreed with NLRB's presumption stating there is no concrete evidence suggesting all replacements are inherently anti-union or that employers who hire them do so out of anti-union animus. Therefore, unless specific proof can be provided showing discrimination against union activities by employers while hiring permanent replacements during strikes, such actions cannot be considered unlawful under federal law.

In the dissenting opinion for the case National Labor Relations Board v. Curtin Matheson Scientific, Inc., Justice Blackmun argued that the majority's decision undermined long-standing precedent and destabilized labor law. He contended that by allowing employers to challenge a union's representative status during economic strikes based on unsubstantiated claims of disloyalty among striking workers, it would encourage more aggressive anti-union tactics from employers and discourage peaceful collective bargaining. Furthermore, he criticized the majority’s reliance on an assumption about human behavior (that employees who cross picket lines are likely to be against union representation) as lacking empirical support or legal reasoning. This approach could potentially lead to unfair labor practices and disrupt industrial peace.