The United States v. Martinez-Fuerte et al., 1975, was a U.S Supreme Court case that addressed the constitutionality of immigration checkpoints. The defendants were charged with transporting illegal aliens within the country and argued that their arrests at permanent immigration checkpoints violated their Fourth Amendment rights against unreasonable searches and seizures. However, the court ruled in favor of the government by a vote of 7-2, stating that these stops are not violations because they serve a vital public interest - controlling movement across borders - which outweighs any minor infringement on individual liberties. Therefore, law enforcement officers can refer vehicles for secondary inspection without needing reasonable suspicion or probable cause to believe an immigration law has been broken.

In the dissenting opinion for United States v. Martinez-Fuerte et al., Justice Brennan, joined by Justice Marshall, argued that routine stops and searches at immigration checkpoints without reasonable suspicion or probable cause violated the Fourth Amendment's protection against unreasonable searches and seizures. They contended that such practices were not justified by a balancing test of governmental interest versus individual rights because they believed there was no empirical evidence to suggest these stops significantly deterred illegal immigration. Furthermore, they expressed concern about potential racial profiling in implementing these checks. The dissenters also disagreed with the majority’s view that motorists' subjective expectations of privacy were less at roadblocks than elsewhere; instead, they asserted individuals should not expect to be stopped and questioned without reason while going about their daily lives.