In the 1974 case Test v. United States, the Supreme Court ruled on whether or not a warrant was required for border searches of international mail. The court held that customs officials did not need to obtain a search warrant before opening and inspecting international mail believed to contain contraband. This decision was based on longstanding precedent recognizing the government's authority to protect its borders by examining incoming international materials without violating Fourth Amendment protections against unreasonable searches and seizures. In this particular case, federal agents had opened an envelope from Thailand addressed to Robert Test which they suspected contained illegal drugs - it indeed contained heroin. The court concluded that such inspections are reasonable given their purpose in preventing smuggling and enforcing immigration laws.

The dissenting opinion in the case of TEST v. UNITED STATES argued that the majority's decision to uphold a law requiring individuals to register for selective service, even during peacetime, was an overreach of federal power and violated individual liberties. The dissenters believed that such registration should only be required during times of war or national emergency. They contended that mandatory peacetime registration infringed upon personal freedoms without sufficient justification from the government about its necessity for national security purposes. Furthermore, they expressed concerns about potential misuse of this system by future administrations and cautioned against setting a precedent where civil liberties could be curtailed under vague notions of public safety or interest.