Brewer signed the bill in a state auditorium about a mile from the Capitol complex where some 2,000 demonstrators booed when county Supervisor Mary Rose Wilcox announced that "the governor did not listen to our prayers."
"It's going to change our lives," said Emilio Almodovar, a 13-year-old American citizen from Phoenix. "We can't walk to school any more. We can't be in the streets anymore without the pigs thinking we're illegal immigrants."
The Mexican American Legal Defense and Education Fund said it plans a legal challenge to the law, arguing it "launches Arizona into a spiral of pervasive fear, community distrust, increased crime and costly litigation, with nationwide repercussions."
William Sanchez, president of the National Coalition of Latino Clergy and Christian Leaders Legal Defense Fund, said his group is preparing a federal lawsuit against Arizona to stop the law from being applied. The group represents 30,000 Evangelical churches nationwide, including 300 Latino pastors in Arizona.
"Millions of Latinos around the country are shocked," Sanchez said.
Mexico has warned the proposal could affect cross-border relations. On Thursday, Mexico's Senate unanimously passed a resolution urging Brewer to veto the law.
"Police in Arizona already treat migrants worse than animals," said Francisco Loureiro, an activist who runs a migrant shelter in the border town of Nogales, Mexico. "There is already a hunt for migrants, and now it will be open season under the cover of a law."
Guatemalan Vice President Rafael Estrada said the law "is a step back for those migrants who have fought" for their rights. Guatemala's Foreign Relations Department decried the measure in a statement saying "it threatens basic notions of justice."
Anyone want to explain why other countries feel they have the right to tell America how to run it borders?