California is again forging its own path on immigration reform by becoming the first state to prohibit landlords from asking tenants' immigration status.

Amid frustration over the federal government's failure to reform immigration laws, cities across the country have taken their own action to keep out illegal immigrants, including barring property from being rented to undocumented tenants.

The law signed this week by Gov. Arnold Schwarzenegger elicited a sigh of relief among landlord associations concerned that without it, they'd be forced to take on the cost and the liability of enforcing federal laws as "de-facto immigration cops," said Nancy Ahlswede, executive director of the Apartment Association, California Southern Cities.

"We have huge anti-discrimination obligations," said Ahlswede, whose organization was among the legislation's sponsors. "We understand the frustration, but that burden shouldn't be placed on landlords."

California has often made headlines by staking new ground on immigration, whether with measures like Proposition 187 — a 1994 ballot initiative meant to deny illegal immigrants social services, health care, and public education — or by kicking off earlier this year the "New Sanctuary Movement," in which churches seek to protect undocumented immigrants from deportation.

This latest law pushes against a national trend that finds tensions over immigration and sh, and pre-empts the federal government's authority.

"If the federal government wants to go after someone, they can do that, but a city can't," said Kristina Campbell, an attorney with the Mexican American Legal Defense and Education Fund, who worked on the lawsuit against Escondido, Calif., which also passed an ordinance punishing landlords who rent to undocumented immigrants.

The suit was settled out of court when costs ballooned, city officials said.

Generally, any proposition that orders those not trained in immigration law to determine whether an immigrant is in the country legally is fraught with potential problems, immigrant advocates said.

The law is complicated and a property owner trying to hazard a guess about someone's immigration status could rely on someone's looks or their accent, leading to discrimination, said Reshma Shamasunder, director of the California Immigrant Policy Center.

Greg McConnell, who has two rental properties and helped organize landlords in Berkeley to support the bill, said he's just glad to be out of the cross-hairs of a "bitter and inflammatory" debate that's much larger than they are.

"It's not a question of where landlords stand on the immigration issue, it's a question of who's to enforce those laws," he said.