Updated: 6:26 p.m.

Former Senate aide Doug Hampton has been indicted on charges that he violated conflict of interest laws — over allegations that he contacted his former boss, Sen. John Ensign (R-Nev.), in violation of the chamber’s “revolving door” rules — the Justice Department announced Thursday.

A federal jury charged Hampton, who served as Ensign’s administrative assistant before leaving Capitol Hill in 2008, with seven counts of violating federal laws. He is scheduled to be arraigned March 31 in the U.S. District Court for the District of Columbia.

An attorney for Hampton declined to comment Thursday.

Ensign acknowledged in 2009 that he had an affair with Hampton’s spouse, Cynthia Hampton, who was a campaign aide.

Doug Hampton has said that Ensign helped him to find lobbying clients after he left the Senator’s office. However, the indictment does not name Ensign, and the Nevada lawmaker’s attorney announced in December that the Justice Department had declined to pursue allegations against Ensign.

According to the Justice Department, Hampton is charged with violating rules that prohibit top Senate aides from lobbying for one year after leaving their post. After quitting Ensign’s office, Hampton became a consultant to two Las Vegas-based companies.

“According to the indictment, between May 1, 2008, and May 1, 2009, while he was subject to The Honest Leadership and Open Government Act’s one-year restriction, Hampton knowingly and willfully made, with the intent to influence, communications to staff members of the U.S. senator on behalf of the Las Vegas airline company and energy company, seeking action by the senator and the staff members in their official capacities,” the Justice Department statement said.

If found guilty, Hampton could face up to five years in prison and a fine of up to $250,000 for each count.

The indictment added that Hampton certified that he had completed ethics training in the Senate, which included information on the one-year ban.

Ensign has faced allegations that he tried to cover up his affair with Cynthia Hampton, and he continues to be the subject of a Senate Ethics Committee investigation. The committee, which began the probe in fall 2009, announced in February that it had hired a special counsel to take over the case.

The Federal Election Commission voted in late 2010 to dismiss a complaint alleging that Ensign violated campaign finance rules over a $96,000 gift that his parents provided to the Hamptons.

Doug Hampton had alleged the funds constituted a severance payment, but the FEC ruled that only Ensign’s parents could attest to the “intent” of the funds, which the couple described as a “gift” in sworn statements.