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A barrier built using damaged buses, erected by rebel fighters of al-Jabha al-Shamiya (the Shamiya Front), which serves as protection from snipers of the forces of Syria's President Bashar Assad, is seen in Aleppo, Syria, April 7, 2015. Reuters/Abdalrhman Ismail

(Reuters) - A Michigan-based Islamist preacher whose online sermons have been a leading source of inspiration for foreign fighters in Syria is free to return to social media after restrictions on his Internet use lapsed.

Officials at the U.S. Attorney's office and federal district court in Detroit told Reuters that probation constraints that a federal judge ordered last summer on imam Ahmad Musa Jebril expired last week.

Those restrictions had included tight controls on his online access and a requirement that the fiery preacher report periodically to probation authorities.

Jebril, a U.S. citizen of Palestinian descent, is now free to preach online again but there has been no sign in recent days that he has posted any videos on Twitter, YouTube or his website. Jebril’s lawyer, Rita Chastang, did not respond to multiple messages requesting comment.

U.S. officials in different agencies have been divided over whether rhetoric used by preachers like Jebril, often couched in religious imagery or symbolism, violates U.S. law or is protected under free speech provisions of the First Amendment to the U.S. Constitution.

A year ago, a London thinktank that specializes in studying Islamist militants described Jebril as one of two English-speaking preachers most favored by foreigners who have joined the fighting in Syria in groups like Islamic State and Jabhat al-Nusra.

The International Centre for the Study of Radicalisation said in a report that instead of directly urging English speakers to join Syrian militants, Jebril "adopts the role of a cheerleader: supporting the principles of armed opposition to (Syrian President Bashar al-) Assad, often in highly emotive terms, while employing extremely charged religious or sectarian idioms."

U.S. federal judge Gerald Rosen last June imposed the tight supervision of Jebril for violating conditions of his early release from a lengthy prison sentence imposed for fraud and jury tampering.

Documents filed in court by the government in the sentencing phase of Jebril's trial alleged that he and his father had a long involvement with Islamic militant groups and ideology.

Federal officials familiar with the case said at the time that although the fraud case was not directly related to Jebril's preaching, the judge's restrictions on his online activity would allow probation authorities to make sure Jebril was not trying to instigate Americans to travel to Syria to join other foreign fighters.

Jebril stopped posting sermons on the Internet within days.

Most of the teachings of Jebril, whose surname is often spelled Jibril, are based on his strict interpretation of Sunni Islamic religious practice. But he has also been a strong supporter of the Islamists in Syria and a harsh critic of moderate Muslims in the West.

"When your brothers in Syria speak, everyone today needs to shut their mouth and listen because they’re proving themselves to be real men," he said in a 2012 online sermon.

Jebril, from Dearborn, Michigan, was jailed in 2005 for crimes committed with his father while running a string of rental properties. Prosecutors said they vandalized some of the properties and filed and collected on bogus insurance claims.

The court made no move to extend Jebril's supervision by probation authorities, according to a court official and Gina Balaya, a spokeswoman for the U.S. Attorney's office in Detroit.