A new ruling by the California State Supreme Court has determined that police don’t need to have a warrant to search through the data on a detainee’s cell phone for evidence to use against him. The ruling, which came as a 7-2 result, was based on a challenge to an arrest of someone attempting to purchase drugs from a police informant. A text message found (which said “6 4 80”) on his cell phone was used as evidence that he tried to sell some drugs as well.

The ruling says that a cell phone is an item of “personal property” and that police are therefore entitled to search all of the data the same way they are entitled to rifle through a detainee’s pockets after this arrest. Experts warn the ruling could be used as a basis for warrantless searches on anything that carries data, including tablet PCs and laptop computers.

The dissenting opinion warned that cell phones are different because they can contain such a large amount of data and that it was inappropriate to give police a blank check to search through the entire contents of the device in hopes of finding evidence.

A 2008 paper from the University of Houston Law Center appears to have forseen this very problem, cautioning that the “search incident to arrest” doctrine, if applied to cellphones, could be used to allow broad warrantless searches without probable cause against people arrested on trivial offenses.