On Wednesday, the U.S. Supreme Court handed a huge victory to privacy rights and Fourth Amendment constitutional protections – and dealt a big blow to the Obama administration’s attempt to trample both – by unanimously ruling that police may not search cell phones without a warrant.

The case stemmed from two opposing lower court rulings in California and Massachusetts. In California, prosecutors used information retrieved from a smartphone without a warrant to convince a jury to convict a defendant of attempted murder, along with other charges. The state courts rejected efforts to have the evidence thrown out and upheld the convictions.

In Boston, police arrested a man on suspicion of selling drugs, used cell phone call logs obtained without a warrant to determine where he lived, and then secured a warrant to search his home where they found drugs, a weapon and ammunition. In this case, the court sided with the suspect, although he was still convicted on drug charges based on evidence properly gathered. The Obama administration petitioned for an appeal, arguing, “It is settled law that a custodial arrest based on probable cause justifies a full search of an arrestee and any items found on him – including items such as wallets, calendars, address books, pagers and pocket diaries.”

In its ruling this week, SCOTUS resoundingly disagreed: “Modern cell phones are not just another technological convenience. With all they contain and all they may reveal, they hold for many Americans ‘the privacies of life,’” wrote Chief Justice John Roberts. “The fact that technology now allows an individual to carry such information in his hand does not make the information any less worthy of the protection for which the Founders fought.” Roberts concluded, “Our answer to the question of what police must do before searching a cell phone seized incident to an arrest is accordingly simple – get a warrant.”

In advocating for the authority to search cell phones without a warrant, police agencies argued doing so is akin to asking a suspect to turn his pockets inside out. But the Supreme Court disagreed, likening it instead to “ransacking his house for everything which may incriminate him.”

The case is bound to become a landmark decision on privacy rights in the 21st century, as the technological saturation of American society has forced examination of constitutional privacy protections in a new (read: old) light. In the U.S. today, nine of 10 adults own a cell phone, more than half of which are smartphones. More than half use their phones to send or receive email and use the Internet, while eight in 10 use phones for texting. The amount of data available on a phone – from calendars and banking information to contacts and health records – is vast. Furthermore, Roberts wrote, “The average smart phone user has installed 33 apps, which together can form a revealing montage of the user’s life.”

The Court conceded that its ruling, which applies to phones’ digital content but still allows examination of phones’ physical characteristics, will impact law enforcement’s ability to combat crime. Yet, the Court stated, “Privacy comes at a cost.”

Indeed, privacy does come at a cost – as does Liberty. But the greater cost comes in sacrificing either for promises of protection that yield only government tyranny.