( CNN ) -- A federal judge has allowed Arizona to enforce the most controversial part of its politically charged immigration law , the so-called `` show me your papers '' provision . In an order on Tuesday , U.S. District Judge Susan Bolton upheld the section allowing authorities , while enforcing other laws , to question the immigration status of people who may be in the United States illegally . The Supreme Court in June tossed out most other aspects of the tough new law but said the part known by critics as the `` show me your papers '' provision could go into effect , at least for now . The hot-button immigration issue is a major attack line in this year 's presidential campaign with Republicans , led by Mitt Romney , accusing President Barack Obama of failing to devise a comprehensive strategy to deal with illegal immigration . Arizona is the nation 's most heavily traveled corridor for illegal immigration and smuggling . The Justice Department said Arizona 's population of two million Latinos includes an estimated 400,000 there illegally , and 60 % to 70 % of deportations or `` removals '' involve Mexican nationals . The Pew Hispanic Center recently issued a report that found that Mexican immigration to the United States has come to a standstill . However , the debate continues as more than 10 million unauthorized immigrants -- from Mexico and other countries -- continue to live in the United States . Bolton 's decision was in response to a suit that followed the Supreme Court ruling by a number of individuals and civil rights groups who said enforcement would lead to racial profiling . It would be up to Arizona to decide when to enforce the measure and there was no sign that would occur immediately . It was not clear if the coalition of civil rights groups and individuals would appeal Tuesday 's ruling or wait to see how the law is enforced . What 's next in the Arizona immigration battle ? `` There is a basic uncertainty about what the law means and how it will be enforced , '' said Supreme Court Justice Anthony Kennedy in late June , making clear that Arizona authorities must comply with federal law in conducting the immigration status checks or face further constitutional challenges . Arizona Gov . Jan Brewer , a Republican who led the fight to pass the overall law , applauded the latest court order , saying it gives law enforcement `` one more tool '' to use `` in collaborating with federal authorities to reduce the crime and other impacts associated with illegal immigration . '' She said the law `` must be enforced efficiently , effectively and in harmony with the Constitution and civil rights . '' The American Civil Liberties Union , which had asked Bolton to block the provision , said it was prepared to continue challenging the law by documenting instances of racial profiling throughout the state , Alessandra Soler , executive director of the legal group in Arizona , said in a statement . The Supreme Court struck down other challenged parts of the Arizona law , upholding the broad authority of the federal government to set immigration policy and laws . Among provisions tossed by the high court was a measure that authorized police to arrest illegal immigrants without a warrant where `` probable cause '' existed that they committed a public offense making them removable from the country . The Arizona law generated immediate controversy after it was signed by Brewer in April 2010 , prompting an Obama administration challenge . Supporters of the Arizona measure contend the federal government has failed to enforce existing immigration laws , leaving it to states to take their own steps to deal with mounting economic and social problems caused by illegal immigrants . Administration officials have said the Department of Homeland Security expects increased requests from Arizona police to check the immigration status of suspects . However , they said the department will get involved only in high-priority cases . Several other states followed Arizona 's lead by passing laws meant to deter illegal immigrants . Similar laws are under challenge in lower courts in Georgia , Alabama , Utah , Indiana and South Carolina . Arizona 's appeal is the first to reach the Supreme Court . At issue was whether states have any authority to step in to regulate immigration matters or whether that is the exclusive role of the federal government . In dry legal terms , this constitutional issue is known as pre-emption . The district court case is U.S. v. Arizona ( 10-cv-1413 ) . Undocumented immigrants face arrest as they proclaim , 'No papers , no fear ' Alabama appeals ruling on immigration law . Immigration lawsuit revives DREAM Act debate .
Arizona is latest in two - year legal battle over tough immigration law . Hot - button immigration issue is key in presidential campaign . Unclear when Arizona legislature is implementing provision of law passed by Democrats .