Los Angeles Mayor Antonio Villaraigosa has signed into law historic new rules requiring porn performers to wear condoms while acting in areas requiring a city film permit.

The law is believed to be the first in the nation by a local government requiring condom use among porn stars, and is significant because L.A.s San Fernando Valley is the capital of the multibillion-dollar porn industry. Many porn companies have voiced opposition to the rule. They say adult films featuring condoms dont sell as well, and say some porn performers on lengthy film shoots prefer not to use condoms. They have threatened to move film shoots outside city boundaries.

The mayors approval was a huge victory for the L.A.-based AIDS Healthcare Foundation, which has waged a lonely battle for years arguing to protect the health of porn performers. Porn production across the industry has been halted several times over the last decade following concerns that adult film performers have been infected with HIV. Two porn performers who were infected with HIV have since become vocal proponents of a mandatory condom policy.

There are a couple of potential loopholes in the ordinance, however. The city ordinance does not apply to filming that occurs on certified sound stages that dont require film permits. And porn studios, which often use homes in the Valley and backyards to film, could opt to move their shoots into L.A. Countys other 87 cities or in unincorporated areas of the county.

The other big question is how the city plans to enforce the new rule.  The city council has asked the Los Angeles Police Department, city attorneys office and the state's workplace safety agency to figure out how to enforce the rule.

The City Council approved the porn ordinance earlier this month, after the AIDS Healthcare Foundation, which wrote the proposed rule, gathered enough signatures to ask voters to decide on the issue during the June election. Feeling that voters would approve the ordinance, the City Council decided to approve the new rule to avoid spending $4 million on a special election.

The AIDS group has already launched a similar signature-gathering drive to mandate condom use through the L.A. County Department of Public Health. They are hoping to get the issue on the ballot for the November election or pressure the L.A. County Board of Supervisors to pass its own measure.

Californias occupational safety and health agency has already stated that porn performers must wear condoms during filming as part of existing rules protecting workers from bodily fluids. But the fines are fairly small and the rule is largely ignored.

Villaraigosa signed the ordinance on Monday.