In Brinegar v. United States, the U.S. Supreme Court upheld a conviction for transporting liquor in violation of state law, ruling that evidence obtained through warrantless searches and seizures by law enforcement officers is admissible if the officer had reasonable cause to believe that a crime was being committed. The case involved an appeal from petitioner Brinegar who argued his Fourth Amendment rights were violated when police stopped him without a warrant and found illegal alcohol in his vehicle based on suspicion alone. However, the court ruled 7-2 against him stating that while citizens have protection against arbitrary invasions of privacy by government officials, these protections must be balanced with society's interest in effective law enforcement procedures.

In the dissenting opinion for Brinegar v. United States, Justice Jackson expressed concern about the majority's interpretation of probable cause and its potential implications on civil liberties. He argued that by lowering the standard of proof required to justify a warrantless search, the Court was effectively eroding Fourth Amendment protections against unreasonable searches and seizures. Jackson contended that this could lead to an increase in arbitrary police power at the expense of individual rights, particularly those belonging to marginalized groups who are often disproportionately targeted by law enforcement. He also criticized what he saw as a lack of clear guidance from the majority on how lower courts should apply their new understanding of probable cause in future cases.