WASHINGTON >> The Justice Department has dropped its probe of retired four-star Gen. John Allen for his role in an alleged illegal foreign lobbying campaign on behalf of the wealthy Persian Gulf nation of Qatar, his lawyer told The Associated Press.

Attorney David Schertler said in a statement today that the Justice Department had informed him that it was closing its investigation of Allen and no charges would be filed. The Justice Department declined to comment but a law enforcement official familiar with the inquiry who wasn’t authorized to speak publicly confirmed the decision on condition of anonymity.

The AP first reported last June that the FBI had outlined a potential criminal case against Allen in a confidential search warrant application that appeared to have been filed in error on a federal courts website. Days later, the former Marine general who oversaw U.S. and NATO forces in Afghanistan resigned as head of the influential Brookings Institution think tank.

Schertler said it was “deeply unfortunate” and “unfair” that the public release of the FBI’s confidential document had damaged Allen’s reputation and livelihood. A Brookings spokesperson did not immediately respond to a request for comment.

The 77-page document detailed Allen’s behind-the-scenes efforts to help Qatar influence U.S. policy in June 2017 when a diplomatic crisis erupted between the gas-rich monarchy and its neighbors. That included traveling to Doha to advise top Qatari officials and then lobbying U.S. officials, the FBI said.

An FBI agent said in an affidavit in support of a search warrant there was “substantial evidence” that Allen had knowingly broken foreign lobbying laws, and had made false statements and withheld “incriminating” documents.

Allen denied any wrongdoing, saying his involvement with Qatar was meant to help benefit the United States.

The federal investigation has previously ensnared Richard G. Olson, a former ambassador to the United Arab Emirates and Pakistan who pleaded guilty to federal charges last year, and Imaad Zuberi, a prolific political donor now serving a 12-year prison sentence on corruption charges.

The Justice Department has made enforcing foreign lobbying laws a higher priority in recent years but suffered some high-profile defeats in contested cases.

Qatar has spent lavishly on its influence efforts in the U.S. and Europe. The country is allegedly behind a massive cash-for-favors corruption scandal currently unfolding at the European Union’s parliament.