WASHINGTON — The Supreme Court ruled Monday that San Diego, California, officials were right to fire a policeman who sold sexually explicit videotapes of himself in uniform.

The unsigned, unanimous opinion reverses a 9th U.S. Circuit Court of Appeals decision in favor of the officer, who sued under the alias John Roe and claimed his free speech rights were violated.

At issue was the scope of the First Amendment, which protects government workers from discharge if their conduct involves a “public concern” rather than personal, job-related issues such as salary or promotions.

“The speech in question was detrimental to the mission and functions of the employer,” justices said in the ruling, noting that Roe “took deliberate steps to link his videos and other wares to his police work, all in a way injurious to his employer.”

Roe was fired in June 2001 after his supervisor discovered the sex videos were being sold on eBay, the giant Internet auction site. The videos showed Roe removing his police uniform and then masturbating.

Roe’s supervisor charged him with violating department policies on unbecoming conduct and ordered him to stop selling the tapes. Roe did, but was fired for disobeying orders after police officials found that his Internet profile on eBay still included references to the videos.

Roe sued, claiming his activity was a “public concern” because the sex videos were made while he was off-duty and away from the workplace, were marketed to a public audience and said nothing about his employment.

Police officials argued for a more narrow reading of “public concern.” They said only issues of political or social importance should be constitutionally protected.

A divided 9th Circuit sided with Roe. It reasoned that the First Amendment was designed to protect the expression of ideas that the “overwhelming majority of people might find distasteful or discomforting.”

The case is City of San Diego et al v. Roe, 03-1669.