Arizona's Gov. Brewer Signs Controversial Immigration Bill

Arizona Gov. Jan Brewer signed a controversial immigration bill into law today that will give local law enforcement greater authority to ferret out and arrest illegal immigrants.

Immediately before signing the bill into law, Brewer said that the legislation "represents another tool for our state to use as we work to solve a crisis that we did not create and that the federal government refuses to fix."

"We in Arizona have been more than patient waiting for Washington to act," Brewer said. "But decades of inaction and misguided policy have created a dangerous and unacceptable situation."

The bill takes effect in 90 days after the current legislative sessions over the next several weeks.

Video: Gov Brewer signs controversial bill.Play

"I firmly believe [the law] represents what's best for Arizona," said Brewer. "Border-related violence and crime due to illegal immigration are critically important issues for the people of our state, to my administration, and to me as your governor and as a citizen."

The signing came just a few hours after President Obama harshly criticized the legislation, calling it "misguided." The president also instructed the Justice Department to examine the Arizona law to see if it would violate civil rights.

Obama criticized the bill at a naturalization ceremony in the White House Rose Garden for active duty service members from 24 countries.

VIDEO: Law requires police to question anyone they think may be here illegally.Play

The president said if Congress fails to enact comprehensive immigration reform at the national level, "We will continue to see misguided efforts opening up around the country."

The absence of a federal resolution of the controversial issue, he said, "opens the door to irresponsibility by others," and he cited "the recent efforts in Arizona, which threaten to undermine basic notions of fairness that we cherish as Americans."

So far this year, Congress and the administration have made little progress in advancing legislation on the issue.

Outside Capitol Building, Crowds Protest Decision

After the signing, crowds outside of the state capitol building erupted in anger. Carrying signs and American flags, they marched nearby, protesting the governor's decision.

Video of president Barack Obama remarks on Arizona immigration case.Play
Obama: Arizona Immigration Law 'Misguided'

Brewer defended the law against claims that it is discriminatory, saying that she had worked for weeks to rework the language to strengthen civil rights protections. The governor also issued an executive order to develop training for state law enforcement to prevent racial discrimination or profiling.

"As committed as I am to protecting our state from crime associated with illegal immigration, I am equally committed to holding law enforcement accountable should this statue ever be misused to violate an individual's rights," she said.

The Arizona law makes it a crime under state law to be in the U.S. illegally and allows police to arrest and question suspected undocumented persons about their status without a warrant. It also criminalizes the transporting of an illegal immigrant anywhere in the state, even if by a family member.

VIDEO:Critics Charge Legal Racial ProfilingPlay

Brewer, who faces a tough Republican primary in August, signed the same bill that former Arizona Gov. Janet Napolitano, a Democrat, vetoed three times.

Brewer was under intense pressure to not sign the legislation. Civil rights groups have decried the sweeping measure as opening the door to racial profiling and sowing distrust between Hispanics and the law enforcement groups charged with keeping them safe. Others said the law will pull resources from fighting more-serious crimes.

Thousands of people wrote or called the governor's office, with a 10-to-one majority opposing the bill, a spokeswoman said.

"I don't think anything has been this extreme until this point," said Bridgette Gomez, a 24-year-old math tutor. "The evil is racial profiling, to think that you're going to always have to show identification. Because I'm tan, I must be illegal."

But supporters of the law, including U.S. Sen. John McCain, R-Ariz., have said it will help solve an illegal immigration crisis the federal government so far has not acted swiftly enough to contain.

Ariz. Immigration Bill Supporters Say They're Enforcing Law

"Illegal is illegal," said the bill's sponsor, Republican state Sen. Russell Pearce. "We'll have less crime. We'll have lower taxes. We'll have safer neighborhoods. We'll have shorter lines in the emergency rooms. We'll have smaller classrooms."

An estimated 10.8 million immigrants live illegally in the U.S., according to the most recent Department of Homeland Security figures. About 460,000 live inside Arizona's borders.

Now that the Arizona bill has become law, it likely will face constitutional challenges.

President Obama said he's instructed the Justice Department to "closely monitor" the situation and "examine the civilian rights" and other implications of the legislation.

The Mexican American Legal Defense Fund (MALDEF) and other groups are also preparing to challenge the legislation.

"The Constitution is pretty clear about having one set of rules," said Thomas A. Saenz, general counsel and president of MALDEF. "Now, you have the state of Arizona coming along and creating an obstacle to federally mandated priorities."

Still, state Sen. Pearce, a former deputy in the Maricopa County Sherriff's Office, which is known for cracking down on illegal immigrants, said he's merely trying to enforce law that's already on the books.

"Illegal is not a race. It's a crime. And in Arizona, we're going to enforce the law ... without apologies," he said. "It's just that simple."

Vulnerable to Legal Challenges?

California attempted to pass a similar measure in 1994 -- Proposition 187 -- that was designed to keep illegal immigrants from using health, education and other social services.

Even though it passed, it was struck down by a federal court on the basis of constitutionality.

Similar legal challenges against Arizona are inevitable, Saenz said, and it will likely end up costing the state millions of dollars.

"Arizona is going to face very serious consequences if it enacts it," Saenz said, comparing it to the experience in California, where the legislation was a "tremendously wasteful diversion of resources."

"There was a palpable impact on international trade to California, in particular," Saenz said. "It became clear over time that Mexican companies began to take their commerce through Texas and other border states because of pervasive hostility."

But it's high time states step up to the plate and do something about illegal immigrants, Pearce said.

"I would think this is a great opportunity to codify states' inherent authority," he said. "We created the federal government. We're in charge. Constitutionally, we have inherent authority. It's time to step up to the plate and start enforcing the law."

This is not the first time Arizona's state laws have come under fire. In 2005, the state made smuggling humans a state crime, and in 2007, it prohibited employers from knowingly hiring illegal immigrants.

Earlier this week, the state House voted for a provision that would require President Obama to show his birth certificate if he wants to be on the state's ballot in the next presidential election.

Before the signing, protesters had hoped to build grassroots momentum to convince Gov. Brewer to veto the bill -- an effort that ultimately failed.

"You hear story after story of youth that don't find out until they're 16 that they are undocumented because their parents didn't tell them," said Alicia Contreras, 26, a student at Arizona State University. "Arizona is ground zero for these type of immigration laws, and as a youth -- high school, college students -- we need to come together."

ABC News' Sunlen Miller, Bradley Blackburn and "On Campus" reporter Lindsey Reiser contributed to this report, along with The Associated Press.