SAN DIEGO — When members of an anti-illegal immigration group offered to sponsor litter cleanup on local roads, they never imagined California officials would offer them an Adopt-a-Highway stretch near a Border Patrol checkpoint on Interstate 5, the main artery carrying illegal migrants north from the U.S.-Mexico border.

On Friday, lawyers for the San Diego Minutemen told a federal judge that the state had no right to rescind the offer after state legislators complained to the California Department of Transportation. The group asked that its blue Adopt-a-Highway sign be put back where it stood without incident for about six weeks until the agency removed it in January.

"We were moved to silence our message in response to pressure from the open border advocates and the Latino caucus," said Minutemen attorney Robert Fuselier.

"It all comes down to one thing: We can't have our speech because if we do, people who don't like it might become unruly and unlawful."

Attorneys for the state contend the sign was removed because of concerns that demonstrators or vandals could create safety hazards for the 160,000 drivers who pass the checkpoint daily and for Minutemen volunteers collecting litter by the roadside.

The Minutemen have had a polarizing influence in San Diego the past several years, achieving hero status among advocates of tightening border restrictions and sparking outrage from immigrant groups who accuse members of harassing migrant workers.

State lawyer Jeff Benowitz told U.S. District Judge William Q. Hayes the Adopt-a-Highway signs amounted to a "thank-you" from the state, not political messages protected under the First Amendment. He said transportation officials planned to end all sponsorship of roads near Border Patrol stations, and had offered to re-assign the Minutemen to a two-mile stretch of state route in a less-trafficked area in eastern San Diego County.

Hayes asked whether the state would continue moving the Minutemen sign if protests followed it.

"It would seem you're saying you're allowing the people who are unhappy with the message to dictate who can be in the program," the judge said.

"We can do that," Benowitz responded. "It is not a public forum."

Courts have found otherwise. In 2005, the U.S. Supreme Court sided with the Ku Klux Klan after Missouri officials sought to bar the group from its Adopt-a-Highway program under a regulation prohibiting groups that deny membership based on race or with a documented history of violence.

State legislators, meanwhile, renamed the contested stretch of highway the "Rosa Parks Highway" in honor of the black woman arrested in 1955 when she refused to give up her seat to a white man on a city bus in Montgomery, Ala.

California assemblywoman Lori Saldana, D-San Diego, said she was considering legislation that would stop the transportation department from accepting new sponsorships until it develops standards governing who qualified to participate in the highway adoption program.

"We want them to say what constitutes a legitimate group," Saldana said after the hearing.

Police searched the home of San Diego Minutemen leader Jeff Schwilk in 2007 during an investigation into alleged vandalism at three migrant camps in San Diego's McGonigle Canyon.

No members of the group were arrested.