Pheonix ? An Arizona congressman urged the Obama administration on Sunday not to cooperate when illegal immigrants are picked up by local police if a tough new state immigration law survives legal challenges.

U.S. Rep. Raul Grijalva, a Democrat, and civil rights activists spoke to thousands of people gathered at the state Capitol and called on President Barack Obama to fight the law, promising to march in the streets and invite arrest by refusing to comply.

“We’re going to overturn this unjust and racist law, and then we’re going to overturn the power structure that created this unjust, racist law,” Grijalva said.

Obama has called the new law “misguided” and instructed the Justice Department to examine it to see whether it’s legal. It requires police to question people about their immigration status — including asking for identification — if they suspect someone is in the country illegally. Opponents say it would lead to racial profiling because officers would be more likely to ask people who look Hispanic.

Supporters have dismissed concerns about profiling, saying the law prohibits the use of race or nationality as the sole basis for an immigration check.