In Sweezy v. New Hampshire, the U.S. Supreme Court ruled in favor of Paul M. Sweezy, a Marxist economist and professor who was held in contempt by the state of New Hampshire for refusing to answer questions about his political beliefs and associations during an investigation into subversive activities under the state's Subversive Activities Act of 1951. The court found that this act violated Sweezy's rights under the First and Fourteenth Amendments to free speech and due process respectively, arguing that academic freedom is a special concern of these amendments which states have no authority to infringe upon arbitrarily or unnecessarily. The decision emphasized that scholars must be free from oppressive government intrusion into their work so they can fulfill their roles in society effectively.

In the dissenting opinion for Sweezy v. New Hampshire, Justice Clark argued that the majority's decision was an overreach of judicial power and a disregard for state sovereignty. He contended that Paul Sweezy had not been denied any constitutional rights during his investigation by the Attorney General of New Hampshire, as he was merely asked to answer questions about his political beliefs and affiliations under oath in front of a grand jury - a common practice in legal proceedings. Furthermore, Justice Clark believed that it wasn't within the Supreme Court's jurisdiction to determine whether or not these questions were relevant to New Hampshire’s inquiry into subversive activities within its borders; this should be left up to individual states. The justice also expressed concern that this ruling could potentially undermine future investigations into potential threats against national security.