In a unanimous decision, the US Supreme Court today said police cannot search cellphones without a warrant during arrests, a major victory for privacy rights groups. The Supreme court decision may set up a more significant privacy fight regarding the National Security Agency (NSA).

NSA Supreme Court

John Roberts: “Privacy comes at a cost.”

In their ruling the justices were clear a tradeoff was at hand. “We cannot deny that our decision today will have an impact on the ability of law enforcement to combat crime,” Chief Justice John Roberts wrote in the opinion for the court. “Privacy comes at a cost.”

The ruling struck down two different cases where lower courts had diverged, which also occurred in two divergent NSA rulings the Supreme Court will likely decide. In California the court struck down a ruling from the state Court of Appeals and in Massachusetts the court upheld a judge’s ruling that threw the search out of court.

Roberts noted the significance of cellphones in modern life with humor. “(Cellphones) are now such a pervasive and insistent part of daily life that the proverbial visitor from Mars might conclude they were an important feature of human anatomy. Modern cellphones are not just a technological convenience,” Roberts wrote. “With all they contain and all they may reveal, they hold for many Americans ‘the privacies of life.’ 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.”

NSA Supreme Court challenge

A USA Today report notes the case could be a precursor to a blockbuster NSA Supreme Court challenge. “The cellphone cases may be just a precursor to more expansive and potentially explosive high court inquiries. Among them: an examination of the National Security Agency’s phone and computer surveillance methods, on which two federal district courts recently diverged.”

The issue is creating new Fourth Amendment issues for police to address, as nine in 10 U.S. adults own cellphones, more than half of them smartphones. Eight in 10 use those phones to send text messages; more than half send or receive e-mail, download applications, or access the Internet – a potential treasure trove for learning about a suspect’s life and past behavior.