Phoenix, Arizona (CNN) -- Hundreds of people gathered outside Arizona's Capitol building on Sunday in a largely peaceful protest against the state's tough new immigration law.
Chanting "Yes we can," waving American flags and holding signs reading "We have rights" and "We are human," demonstrators kept up a festive spirit as they denounced the bill signed Friday by Gov. Jan Brewer.
The new law requires police to determine whether a person is in the United States legally. It also requires immigrants to carry their alien registration documents at all times and requires police to question people if there is reason to suspect they're in the United States illegally.
Protesters worry that the law will foster racial profiling.
"What is 'reasonable suspicion?' " protester Jose Acosta asked Sunday. "Are we going to get pulled over just because of a broken taillight or because of the color of our skin? ... If so, is everybody going to be pulled over?"
Kearny Police Chief Joe Martinez called critics' concerns unfounded, saying the Arizona law enforcement community includes a large number of Hispanics.
"We've never had a policy of racial profiling," Martinez said Saturday night at a town hall meeting in Casa Grande. "In fact, quite the contrary, it's been outlawed."
Phoenix Mayor Phil Gordon appeared at the rally in support of the protest, calling the law unconstitutional and "just plain wrong."
"America is a country that is compassionate and that welcomes everyone," he said. "This is not what this country and this state was founded upon."
Gordon vowed to take the fight through the state's judicial system.
"We'll go to the state courts and we'll go to the federal courts and we'll go all the way to the Supreme Court," he told the cheering crowd. "I promise you."
Gordon told CNN on Saturday that he will bring up an item calling for legal action against the law at Tuesday's City Council session.
Others were also vowing this weekend to legally challenge the law.
The Rev. Al Sharpton, along with leaders from the National Action Network and the Hispanic Federation, announced Sunday that he will legally challenge the law.
The law "is an affront to the civil rights of all Americans and an attempt to legalize racial profiling," Sharpton said in a statement after the bill's signing Friday. "As one who helped to make racial profiling a national issue and who has in the last year visited Arizona several times to rally against these draconian immigration policies, I am calling for a coalition of civil rights organizations to work with those in Arizona to resist and overturn this state law."
The National Coalition of Latino Clergy and Christian Leaders, a group that represents 30,000 Latino churches worldwide, also said Saturday it plans to file a lawsuit against the bill.
"In addition to this law being illegal, if this law goes into effect, we expect it to have a dramatic affect on the state with U.S. citizens, legal residents and others moving out of the state out of fear of being singled out," William Sanchez, an immigration attorney representing the coalition, said in a statement.
CNN's Casey Wian contributed to this report.