President Felipe Calderon told a Mexico City news conference Monday the Arizona law opens the way for "intolerance, hate, discrimination and abuse in law enforcement."
Arizona Gov. Jan Brewer signed the Support Our Law Enforcement and Safe Neighborhoods Act into law Friday. It takes effect 90 days after the end of the legislative session and authorizes police to check foreigners' identification and detention of those questioned who don't have proper documentation. The measure has sparked demonstrations nationwide, with parallels drawn to the early days of Nazi Germany.
The Foreign Affairs Ministry advised Mexican nationals to use "extreme caution" traveling to Arizona -- even before the law takes effect -- and listed consulates where people can get help.
"It is important to act with prudence and respect local laws," the advisory said.
It added, "As long no clear criteria are defined for when, where and who the authorities will inspect, it must be assumed that every Mexican citizen may be harassed and questioned without further cause at any time."