Though several immigration issues simmer in California, Democratic Gov. Gray Davis' (search) signature Friday on a bill allowing illegal aliens to obtain a legal California driver's license has sparked considerable controversy.

Aside from the political debate, and the oxymoron it creates — that it is now legal to be illegal — police have major security concerns.

One such concern is the sale of fraudulent identification forms. Under the new law, illegals must present two forms of identification to the state's Department of Motor Vehicles.

Places like Los Angeles' MacArthur Park (search) have become a marketplace for fake IDs, including foreign birth certificates and the matricula consular (search) card, the card issued by the Mexican consulate. Spurred on by the Mexican government, dozens of American cities now accept the matricula consular cards as legitimate identification.

Fox News sent a buyer out who easily purchased a card for $90. Come January, experts say, it will be no problem to use the card to get a legitimate California license.

Advocates of the new law downplay the potential for fraud and say the bill makes roads safer by requiring illegals to take a driving test. Critics say the roads may be safer, but the county is not.

"In California, you can now obtain a gun, explosives, jobs in secure areas — even at a nuclear power plant" — with a driver's license, an undercover officer who is a document fraud expert told Fox News.

Some lawmakers say even if Mexicans aren't a terror threat to the United States, foreigners from hostile countries could try to pass themselves off as Mexican to get the documents they need to legally enter U.S. society. Rep. Elton Gallegly, R-Calif., said he doesn't understand why U.S cities are even accepting matricula consular cards as eligible ID.

"What about Syria? What about Iran? Where do we draw the line?" Gallegly asked. "Are we going to say it's OK this country does it? The bottom line is, the only people that need this are people that have no legal right to be here to begin with."

In the past, matricula consular cards were only given to legal residents in the United States. Mexico changed that last year, giving them to any Mexican national — legal or not — who requested one. Mexican officials say the question of whether the U.S. should accept them is a debate for the U.S. politicians, not the Mexican government.

"That is not my problem, it is the problem of the United States. Our problem is to protect the Mexicans. The obligation, the task of all the consulates, 47 consulates around the country, is to protect the Mexicans who live here," said Agustin Pradillo, a diplomat at the Mexican consulate in Los Angeles.

The U.S. Congress may step in and work on legislation that says the only acceptable foreign identification is a passport. Because of security concerns, some states may also decide not to accept California driver's licenses as ID, saying the new law there sends the message that immigration rules are meaningless.

Fox News' William La Jeunesse contributed to this report.