The Lincoln Federal Labor Union et al. v. Northwestern Iron & Metal Co. et al., 1948, was a landmark case that revolved around the constitutionality of Nebraska's "Right to Work" law which prohibited employers from requiring union membership as a condition for employment (closed shop agreements). The Supreme Court ruled in favor of the labor unions, declaring that Nebraska's law violated the National Labor Relations Act (NLRA) by infringing on workers' rights to organize and collectively bargain with their employers. This ruling affirmed federal supremacy over state laws regarding labor relations and reinforced protections for organized labor under federal legislation.

In the dissenting opinion for Lincoln Federal Labor Union v. Northwestern Iron & Metal Co., Justice Frankfurter disagreed with the majority's decision to strike down a Nebraska law prohibiting union membership as a condition of employment, arguing that it was not within the Court's jurisdiction to do so. He believed that such decisions should be left up to individual states and their legislatures rather than being dictated by federal courts. Furthermore, he argued that there was no clear constitutional violation in this case since both employers and employees were free to negotiate terms of employment without government interference. In his view, unions did not have an inherent right under the Constitution or federal law to require compulsory membership from workers as part of their contracts with employers.