In what may become one of this year’s most far-reaching court rulings, the U.S. Supreme Court ruled unanimously today that a right to privacy applies to cell phones, and that law enforcement cannot inspect the contents of cell phones without a search warrant. Chief Justice John Roberts, one of the high court’s five conservatives, wrote the opinion, which you can read in full here. Good summaries include David Savage’s report for the Los Angeles Times, Adam Liptak’s report for the New York Times, and this SCOTUSblog analysis by Lyle Denniston:

The Court rejected every argument made to it by prosecutors and police that officers should be free to inspect the contents of any cellphone taken from an arrestee.  It left open just one option for such searches without a court order:  if police are facing a dire emergency, such as trying to locate a missing child or heading off a terrorist plot.  But even then, it ruled, those “exigent” exceptions to the requirement for a search warrant would have to satisfy a judge after the fact.

The ruling was such a sweeping embrace of digital privacy that it even reached remotely stored private information that can be reached by a hand-held device – as in the modern-day data storage “cloud.”  And it implied that the tracking data that a cellphone may contain about the places that an individual visited also is entitled to the same shield of privacy.

I’m not surprised by the decision, but I’m surprised it was unanimous. It’s a very strong statement that police need to change their standard practices after arresting suspects will have to change.