aliensAs Arizona prepares to implement a controversial law cracking down on illegal immigrants, the American Civil Liberties Union has issued a travel alert advising visitors to the desert state of their civil rights if stopped by police.

The law requires state and local police to investigate the immigration status of anyone that they reasonably suspect is in the country illegally, during the course of lawful contact such as a traffic stop.

Backers of the measure, which takes effect on July 29 barring a successful legal challenge, say it is needed to curb illegal immigration and border-related crime in the state, which is a major corridor for drug and human smuggling from Mexico. Opponents, among them the ACLU, say it is a recipe for racial profiling.

“Under Arizona’s racial profiling law, people who look ‘foreign’ are more likely to be stopped for minor infractions and then asked for their ‘papers’ if police believe, based on their appearance or accent, that they could be in the country unlawfully,” Anthony D. Romero, the ACLU’s executive director said in a statement.

“We hope the alerts provide people with some measure of protection from illegal harassment from law enforcement and inform them of their rights should they encounter it,” he added.