The last three states to allow illegal immigrants to obtain driver's licenses -- Washington, New Mexico and Utah -- are now steeped in battles to revise their laws as a federal deadline approaches for all 50 states to issue identity cards that meet a new national standard.

States must be in compliance by May with the regulations laid out in the 2005 REAL ID Act. The law, a recommendation of the Sept. 11 commission that investigated the 2001 terror attacks, creates a national security standard for state-issued identification cards to be used for purposes like boarding airplanes and entering federal buildings.

Originally intended as a counterterrorism tool, REAL ID has had an unintended side effect that has won support of immigration enforcement advocates -- it requires driver's licenses issued to immigrants to expire at the same time as their stay in the U.S., invalidating the licenses of immigrants who overstay their visas.

"You are making (it) very difficult for them to assimilate," said Janice Kephart, director of national security policy at the Center for Immigration Studies said of illegal immigrants. "The inability to assimilate plus enforcement will drive a natural attrition over time."

Christian Gleim, director of policy and communications at the Coalition for Secure Driver's License, said the regulations, combined with more than $100 million in grants to states, have already led to "remarkable improvements" in driver's license procedures in more than 40 states and Washington, D.C.

"The most important improvements have been in increasing scrutiny of identity claims by applicants," Gleim said. "In addition to making it more difficult for foreign terrorists to get state issued driver's license and IDs, it has made it much more difficult for common criminals to game the system. As a result, thousands of imposters have been detained by police and hundreds have been prosecuted and convicted."

But not everyone is sold on the idea that  "national ID standards" will serve as a deterrent to illegal immigration.

Illegal immigrants "didn't come here for a driver's license," said Ira Mehlman, a spokesman for the Federation for American Immigration Reform (FAIR), who nonetheless praised the move toward tighter driver's license rules but argued it will not fix the broken immigration system.

"One reason why we have such large scale illegal immigration is because we've made it so easy. ... We say, 'Don't come to the U.S. but as long as you're here, we'll give you what everybody else has,'" Mehlman said.

Immigration advocates are pushing for a repeal of the REAL ID Act, saying the license programs for undocumented workers provide public safety because unlicensed drivers usually do not carry auto insurance.

"The most common argument you hear against it is it's an argument of attrition -- if we make their lives miserable, the undocumented will go away," said Christine Neumann-Ortiz, director of Voces de la Frontera.

"I think that argument doesn't stand up to reality when you look at states like California where a majority of undocumented immigrants have had no access to driver's licenses," she said. "The undocumented do not go away. The only consequence of those state policies is you have more unlicensed, uninsured drivers on the road because by and large, public transportation is not as convenient as it is in other parts of the world."

Many states, including Maryland, Michigan, Oregon, Wisconsin and Hawaii, have repealed laws enabling illegal immigrants to acquire licenses, and experts say harder line approaches toward illegal immigration in Arizona and elsewhere has pushed illegals into states with lower thresholds for enforcement.

Melissa Savage of the National Conference of State Legislatures, said it's possible that some states could begin offering a two-tiered licensing system so illegal immigrants can still have driving privileges.

"If you go back to the core reason for driver's licenses and making sure people have a record, if that's a priority, that's the one reason," she said.

As for the remaining states that allow illegal immigrants to obtain licenses, all three are working on new legislation.

After a surge in applications from out-of-state illegal immigrants, Washington late last year tightened its requirements for issuing driver's licenses in an effort to reduce the number of people who acquired them fraudulently. Now, the Democratic-controlled Senate is considering a bill that would require applicants for driver's licenses to prove they are in the country legally. The bill is under review in the Senate Transportation Committee.

In Utah, which last year became the only state to offer a special class of driver's licenses for illegal immigrants, the Republican-controlled Senate is considering a bill that would eliminate the state's driving privilege card by the end of the year. The card, which doesn't allow people to board a plane, get a job or buy alcohol, is held by nearly 42,000 illegal immigrants since the statehouse established the option six years ago largely to provide a way for non-citizens to obtain auto insurance.

In the Democratic-controlled New Mexico Legislature, a House committee last week rejected, on a party-line vote, a bill that would have allowed illegal immigrants to have annually renewable driving permits, which would not serve as a form of identification. Democrats on the committee supported the effort to shelve the bill, effectively dooming it for the session.

New Mexico Republican Gov. Susana Martinez, who did not support the bill, said she wants legislation that would stop the licensing practice and cancel more than 80,000 licenses given by the state to foreign nationals. The state contends it doesn't know how many of the licenses have gone to illegal immigrants because it does not ask the immigration status of license applicants.