FILE PHOTO: U.S. Republican presidential candidate Donald Trump is joined onstage by Maricopa County Sheriff Joe Arpaio (L) at a campaign rally in Marshalltown, Iowa January 26, 2016, after Arpaio endorsed Trump's candidacy. REUTERS/Brian Snyder/File Photo

PHOENIX (Reuters) - A federal judge on Wednesday upheld President Donald Trump’s pardon earlier this year of 85-year-old former Arizona Sheriff Joe Arpaio, rejecting legal challenges by outside groups.

U.S. District Judge Susan Bolton said that she had considered the petitions filed by the American Civil Liberties Union of Arizona and other organizations, including one staffed by lawyers who worked for former Democratic President Barack Obama’s administration, but found no legal grounds to overturn the pardon.

Bolton did not rule on a request by Arpaio’s attorneys to take the further step of vacating his conviction.

Trump, a Republican who has promised to build a wall along the U.S. border with Mexico, has praised Arpaio’s crackdown on illegal immigrants in Maricopa County, Arizona, that drew condemnation from civil rights groups.

Arpaio was convicted in July of willfully violating a 2011 injunction barring his officers from stopping and detaining Latino motorists solely on suspicion they were in the country illegally. He had not yet been sentenced when Trump issued the pardon in August.