In Watkins v. United States (1956), the U.S Supreme Court ruled in favor of John T. Watkins, an Ohio labor organizer who was convicted for contempt of Congress after refusing to answer questions about individuals he allegedly knew to be members of the Communist Party during a hearing before the House Un-American Activities Committee (HUAC). The court held that Congressional investigations must not infringe upon citizens' First Amendment rights and are only legitimate if they serve a legislative purpose. It further stated that HUAC had failed to clearly define its authority and purpose in questioning Watkins, thus violating his constitutional right against self-incrimination under Fifth Amendment protections. This case marked a significant limitation on the power of Congressional committees and set important precedents regarding individual rights during congressional investigations.

In the dissenting opinion for Watkins v. United States, Justice Felix Frankfurter argued that the majority's decision was an overreach of judicial power and a misinterpretation of Congressional intent. He contended that Congress had clear authority to investigate matters related to potential legislation, including inquiries into subversive activities threatening national security. The Un-American Activities Committee's investigation into Communist infiltration fell within this scope according to him. Furthermore, he asserted that it was not the Court’s role to question or limit what Congress deemed necessary in its investigations unless there were explicit violations of constitutional rights which wasn't evident here as per his view. He also expressed concern about how this ruling would impact future congressional investigations and potentially hinder them from fulfilling their legislative duties effectively.