Because of this expectation, employers don't have the right to read employees text messages without the employee's knowledge and consent, a three-judge panel of the 9th Circuit Court of Appeals' unanimously ruled in an appeal in a lawsuit filed Ontario, Calif., by Police Sgt. Jeff Quon and three others against the city's service provider, the city and its police department for violating the workers' right against unreasonable searches.

The city told employees it may monitor their e-mails, but the informal policy was that text messages sent over city-owned pagers wouldn't be monitored for content, the court said. If an employee ran over the city's limits on messages, the employee paid "overage" charges.

When Quon exceeded the limit, the police chief ordered a transcript from the communications provider, Arch Wireless, which complied.

The court noted Quon exceeded the 25,000-character limit several times and paid for the overages without anyone reviewing the content of the messages.

"The search of appellants' text messages violated their Fourth Amendment and California constitutional privacy rights because they had a reasonable expectation of privacy in the content of the text messages, and the search was unreasonable in scope," the panel wrote.