San Fransico — County officials in Seattle can prohibit an advertisement criticizing Israeli policies toward Palestinians from appearing on local buses without violating constitutional protections on free speech, a U.S. appeals court said on Wednesday.

In a 2-1 ruling, the 9th U.S. Circuit Court of Appeals in San Francisco found that King County acted reasonably when it barred the ad, which sparked threats of vandalism and violence that could have endangered passengers.

The American Civil Liberties Union of Washington, which helped challenge the ban, is disappointed in the ruling, Executive Director Kathleen Taylor said.

“The government should not be able to suppress speech because it arouses passionate debate,” Taylor said in a statement. “Sadly, King County allowed its fear of controversy to trump a commitment to free speech.”

Harold Taniguchi, director of the county transportation department, said in a statement that the county was “pleased the court found that our actions to ensure the safety of our passengers were reasonable.”

In 2010, a non-profit group opposed to U.S. support for Israel proposed a bus ad that read: “ISRAELI WAR CRIMES YOUR TAX DOLLARS AT WORK,” along with a website address. The county originally flagged the ad as controversial, but decided it did not violate bus advertising policy and approved it.

After a local news broadcast about the impending ad, officials faced a public furor. Photos depicting dead or injured bus passengers appeared under the door of a transportation authority service center, the ruling said.

The county eventually rejected that ad, along with others proposed by pro-Israel groups. The pro-Palestinian Seattle Mideast Awareness Campaign sued and a judge in a lower court sided with the county.

In dissent, Judge Morgan Christen said that while safety is a concern, “it also may be that the county inappropriately bowed to a ‘heckler’s veto’ and suppressed speech that should have been protected.”

She said the case should have been sent back to the lower court for more fact-finding.