"This is an early Christmas statement," Ensign told the Las Vegas Review-Journal.
That's two bits of good news in a row for Ensign: Just two weeks ago, the Federal Elections Commission dismissed a complaint against the senator.
The Senate Ethics Committee is still investigating Ensign.
The DOJ does not comment on investigations.
The investigation stems from a sex-and-lobbying scandal centered on Ensign and two former staffers. The probe touched other lawmakers, including Sen. Tom Coburn (R-OK), who turned over emails between him and Ensign, and Ensign's staff. Ensign recently set up a legal defense fund and has paid some of his staffers' legal bills.
Last year, Ensign admitted to having an affair with a former staffer, Cynthia Hampton. Hampton's husband, Doug Hampton, was also a high-level staffer and close friend of Ensign.
Eventually both resigned. Ensign allegedly helped Doug Hampton set up as a lobbyist and get clients -- an apparent violation of the one-year lobbying ban in the Senate. The DOJ investigation reportedly focused on that aspect of the scandal, with staffers reportedly testifying that Ensign knew he was breaking the ban when he helped Hampton.
In the final twist, Ensign's parents gave a total of $96,000 to the Hamptons.
Some, including the watchdog Citizens for Responsibility and Ethics in Washington, said the gift amounts to a severance payment for the couple and, as such, was an illegal in-kind contribution to Ensign's committee.
CREW's complaint to that effect with the FEC was thrown out this month. The FEC said in a letter that, because Ensign's parents had said the money was intended as a gift, there was no more the agency could do to prove it wasn't.
For much, much more on Ensign, go here.