George Papadopoulos, a former adviser to President Trump’s campaign, was released from a Wisconsin prison Friday morning.

Papadopoulos served 12 days for lying to FBI investigators about his contact with people linked to Russia during the 2016 campaign.

He left the Federal Correctional Institution in Oxford, Wis., shortly before 10 a.m. EST, according to CNN.

Papadopoulos was told by a Maltese professor in London in 2016 that the Russians had damaging information on Democratic presidential nominee Hillary Clinton. He told an Australian diplomat about the conversation, who then told American officials, initiating an investigation into Trump’s campaign and Russia.

Lawyers for the former Trump campaign adviser had asked a federal judge to delay the prison sentence until a constitutional challenge to the appointment of special counsel Robert Mueller is decided. The lawyers said a case before a panel for the U.S. Court of Appeals for the D.C. Circuit that challenges the constitutionality of the appointment of Mueller could invalidate Papadopoulos’ conviction.

That case involves a former assistant to Roger Stone, a longtime Trump adviser. The assistant, Andrew Miller, has refused to comply with a subpoena to testify to Mueller’s grand jury, arguing that Mueller’s authority is too broad, there’s not enough oversight from the Justice Department, and that Mueller needed Senate confirmation.

In the months after Papadopoulos pleaded guilty, he alleged he had been set up by Western intelligence agencies.

“Still can’t believe the day I am going to a federal prison camp, mainstream media says am going for my Russia contacts. I have never met a single Russian official in my life. I have, however, met many western intel sources—Joseph Mifsud—who people still call ‘Russian.’ Facts. USA,” he wrote in a tweet before serving his sentence.