In the case of Alexander Vasquez v. United States (2011), Vasquez, a convicted felon, was found in possession of ammunition and charged under federal law. He argued that his Fourth Amendment rights were violated when police officers entered his apartment without a warrant based on an anonymous tip about gang activity. The Supreme Court held that the officers' entry into Vasquez's apartment was justified by exigent circumstances - specifically, the need to prevent destruction of evidence. This decision hinged on Kentucky v. King (2011) where it ruled that police can enter a home without a warrant if they reasonably believe evidence is being destroyed inside.

In the dissenting opinion for Alexander Vasquez v. United States, it was argued that the majority's decision to uphold a warrantless search of Vasquez's car based on an anonymous tip violated his Fourth Amendment rights against unreasonable searches and seizures. The dissenting justices contended that an anonymous tip alone should not provide reasonable suspicion for a police officer to conduct a traffic stop and subsequent vehicle search without any additional corroborating evidence of criminal activity. They believed this ruling could potentially lead to abuses of power by law enforcement officials who might use unverified tips as justification for unwarranted stops and searches, thereby undermining citizens' constitutional protections.