Allen was first netted by the FBI in 2006 as part of a wide-ranging probe into corruption in Alaska. He plead guilty to bribery, tax evasion, and other charges in 2007. But his cooperation with investigators, including his role as the star witness in the botched Stevens trial, kept him out of prison.
The former chief executive of oil field services company VECO, Allen was sentenced to three years in prison and fined $750,000 in October.
Part of the investigation focused on Allen's advocacy for construction of a North Slope pipeline in Alaska.