Celebrity private eye Anthony Pellicano, whose clients once included Elizabeth Taylor and Michael Jackson, was sentenced to 2½ years in federal prison Friday for possessing firearms and explosives.

Pellicano, who was also fined $6,000, remains the subject of a grand jury investigation into whether he may have conducted illegal wiretaps of celebrities. Federal officials have declined to provide details of the investigation, and Pellicano has said he is refusing to cooperate.

His career collapsed last year after investigators raided his office, seeking evidence to link him to threats made against a Los Angeles Times reporter. Two practice hand grenades, altered and filled with flash powder, were found in a safe along with military explosive and detonators.

Pellicano, 59, pleaded guilty in October to a felony count of possessing unregistered firearms and a felony charge of possessing C-4 explosive. He agreed to begin serving his prison term in November, although he had not yet been sentenced.

Last month, he sought to withdraw his plea on the firearms count, citing a recent U.S. appellate court ruling that Congress lacked authority to regulate homemade weapons — such as the modified grenades.

“He will be sentenced on an offense that does not exist,” Pellicano’s lawyer, Donald Re, argued Friday.

U.S. District Court Judge Dickran Tevrizian rejected the request, ruling that Congress had the authority to regulate weapons under its taxing power.