The nation's top civil liberties group on Wednesday issued travel alerts for Arizona, saying the state's new law cracking down on illegal immigrants could lead to racial profiling and warrantless arrests.

American Civil Liberties Union affiliates in Arizona, New Mexico and 26 other states put out the warnings in advance of the Fourth of July weekend. The Arizona chapter has received reports that law enforcement officers are already targeting some people even though the law doesn't take effect until July 29, its executive director said.

The alerts are designed to teach people about their rights if police stop and question them.

The Arizona law requires police, while enforcing other laws, to question a person's immigration status if officers have a reasonable suspicion that the person is in the country illegally. It also makes it a state crime for legal immigrants to not carry their immigration documents and bans day laborers and people who seek their services from blocking traffic on streets.

Attorneys defending the law against constitutional challenges filed by the ACLU and others argue that the Legislature amended it to strengthen restrictions against using race as the basis for questioning by police. Five lawsuits are pending in federal court, and the U.S. Justice Department is believed to be preparing a legal challenge.