A California police department did not violate the privacy of a SWAT sergeant, when it reviewed text messages sent using his department-issued pager, the U.S. Supreme Court ruled today.

The Ontario Police Department fired Sgt. Jeff Quon after an internal audit determined he had sent a flurry of personal text messages using his department-issued pager. The ruling does not cover private companies.

The case came about after the agency's wireless carrier, Arch Wireless, provided transcripts of Quon's messages from August and September of 2002, after the sergeant exceeded his monthly allowance on multiple occasions. The department, which did not obtain a warrant prior to the search, determined that many of Quon's messages were not work related, and some were sexually explicit.

The matter was referred to internal affairs, which completed an investigation. Quon was then fired.

The court today unanimously ruled the search to be reasonable and in keeping with the Fourth Amendment, which "guarantees a person's privacy, dignity, and security against arbitrary and invasive governmental acts," according to the ruling.

The court ruled the chief-ordered audit was justified because the agency was seeking to determine whether its messaging plan met the needs of the department, due to the overages, the court ruled.

Messages sent by Quon while off duty were redacted and not reviewed by the department, and the court found that Quon's behavior established a "limited privacy expectation" due to the personal nature of the messages sent while on duty.

Read the New York Times coverage of the ruling.