A federal appeals court ruled Tuesday that officers with the Maricopa County Sheriff’s Department in Arizona must discontinue Sheriff Joe Arpaio’s policy of detaining people they suspect of being undocumented immigrants.

The 9th Circuit Court of Appeals ruling sided with a lower court’s order last December, which required Arpaio end the potentially discriminatory practice pending a lower court’s ruling on a class action lawsuit. Arpaio lost the appeal on strict constitutional grounds, with judges pointing out that the power to enforce immigration laws rests solely with the federal government.

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The three judge panel’s ruling did not address whether Arpaio and his department engaged in racial profiling, but that question is expected to be answered by a judge presiding over Maricopa County police could a class action lawsuit filed against Arpaio by the American Civil Liberties Union of Arizona in 2007.

Plaintiffs in that suit say they have “voluminous evidence” of racial profiling in Maricopa County, including internal memos featuring Arpaio ranting about focusing police resources on “dark skin” individuals. A judge in Phoenix is expected to issue a verdict on that class action suit any day now.

The U.S. Department of Justice also sued Arpaio in May after a three year investigation, alleging he engaged in “a pattern or practice of unlawful discriminatory police conduct direct at Latinos in Maricopa County.”

The self-proclaimed “toughest sheriff in America” has endorsed Republican presidential candidate Mitt Romney, who earlier this year said he supports immigration policies that make life so miserable for the undocumented population that they “self deport.” Arpaio also claimed earlier this year to have unearthed proof that President Barack Obama’s birth certificate is a forgery, even though officials in the president’s birth state of Hawaii have repeatedly verified that it is authentic.