The Ohio Supreme Court has struck an important blow for privacy rights, ruling that the police need a warrant to search a cellphone. The court rightly recognized that cellphones today are a lot more than just telephones, that they hold a wealth of personal information and that the privacy interest in them is considerable. This was the first such ruling from a state supreme court. It is a model for other courts to follow.

Searches generally require warrants, but courts have carved out limited categories in which they are not needed. One of these is that police officers are allowed, when they arrest people, to search them and the area immediately surrounding them, as well as some kinds of containers in their possession.

When the police arrested Antwaun Smith on drug charges they seized his cellphone and searched it, examining his call records. The police did not have a warrant or the consent of Mr. Smith.

The Ohio Supreme Court ruled this month, by a 4-to-3 vote, that the search violated the Fourth Amendment’s protection against unreasonable search and seizure. Rather than seeing a cellphone as a simple closed container, the majority noted that modern cellphones  especially ones that permit Internet access  are “capable of storing a wealth of digitized information.”