The Constitution's Fourth Amendment protects against "unreasonable searches and seizures."
But the Supreme Court has repeatedly affirmed the government's discretion to conduct warrantless initial pat-downs and searches of people and vehicles -- to ensure officers' safety and prevent destruction of evidence.
That included a 1973 ruling upholding the police search of a suspect's crumpled cigarette box, where heroin capsules were discovered. The motorist had first been stopped on suspicion of driving on a suspended license in Washington.
Similar law enforcement searches can include other closed containers, such as wallets and address books, even if it is not initially apparent the items are contraband or dangerous.
But privacy advocates and defense attorneys had argued that portable, easily storable technology makes these appeals different. The court, in sweeping terms, agreed.