Birkenfeld, who had been living in Europe for years before his cooperation with the U.S. government and his subsequent prison sentence, had filed a motion with the U.S. District Court for the Southern District of Florida asking for the terms of his probation—scheduled to end next fall—to be modified to allow him to return to Europe and begin rebuilding his life.
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But the Department of Justice objected to that move, and a judge ruled against Birkenfeld this month. So now Birkenfeld is crying foul in a motion filed with the same court on Tuesday, arguing that other participants in Swiss bank fraud—who did not turn over information on thousands of alleged American tax scofflaws—have been treated far more leniently.
The case boils down to an argument by Birkenfeld that although he voluntarily came to the U.S. government with inside information on Swiss bank secrecy that broke the back of that long-running institution, Birkenfeld has been treated more harshly than a number of the players in the tax fraud he exposed.
In the motion filed Tuesday, Birkenfeld's attorney argues that former UBS client Igor Olenicoff, "with undisclosed Swiss bank assets of approximately $200 million," was sentenced to only two years of probation but was allowed by the government to "attend the wedding of an old grade-school friend getting married on the Greek island of Paros."
Similarly, Birkenfeld's attorney argues, the government "expressed no opposition to a request for early termination of probation filed by John McCarthy, a UBS account holder convicted, as a result of Mr. Birkenfeld's cooperation, of failing to disclose his Swiss bank accounts of more than $1 million."
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Worse, in Birkenfeld's view, is the treatment of Martin Liechti, the former head of UBS wealth management for the U.S. and the Western Hemisphere. Birkenfeld's attorney says Liechti received a nonprosecution agreement from the U.S. government. "As a result," Birkenfeld's lawyer argues, "Mr. Liechti, unlike Mr. Birkenfeld, never had to serve a day in prison, probation or supervised release."
U.S. District Judge William Zloch denied Birkenfeld's earlier request to leave the United States, after the Department of Justice filed its objection.
—By CNBC's Eamon Javers.