It has been highly debated but today the state of Arizona began to enforce the most contentious section of the state's immigration law, making it the first time officers can stop someone using the so-called" show me your papers" provision.
The measure is part of a broad crack-down on illegal immigration in the state signed into law in 2010 by Arizona's Republican Governor , an outspoken critic of President Barack Obama's administration over federal policies on the issue.
The Obama administration challenged the Arizona immigration law in court two years ago, saying the Constitution gives the federal government sole authority over immigration policy, but the U.S. Supreme Court upheld the "show-your-papers" measure.
Opponents of the law complained that it amounted to a mandate for racial profiling of Hispanics, who make up nearly a third of Arizona's 6.5 million people.
Officials said they would check people's immigration status when officers call. But they'll only send an agent to arrest someone if it fits with their priorities. Still, civil rights advocates say they are preparing for a battle.
Arizona has one of the business illegal entry points in the country, five other states are now considering similar laws.