Two years ago, in an effort to slow the relocation of senior Capitol Hill staffers onto K Street, Congress adopted new ethics rules banning them from lobbying the entire Senate for one year.

Under the Honest Leadership and Open Government Act, staffers earning at least 75 percent of their bosses’ salaries for more than 60 days trigger the lobbying moratorium.

According to Senate public records, 211 staffers who met the salary level — individuals whose annual rate of pay was equal to $126,975 or more for at least 60 days during the past 12 months — have left the Hill this year.

But the rule has also ensnared at least one unwitting junior Senate staffer whose $8,000 bonus unexpectedly triggered the lobbying restrictions.

“You can be subject to those rules inadvertently,— said Caplin & Drysdale’s Joseph Birkenstock, a lawyer for the staffer, who declined to be named.

Birkenstock wrote to the Senate Ethics Committee on behalf of his client at the end of June asking for guidance on the Senate rule.

The former Senate staffer earned $80,000 a year, and his $8,000 bonus was paid out over 61 days. When that two-month salary figure was annualized, it brought his yearly pay to just over the $126,975 figure at which the lobby ban is triggered.

“Neither the Senate Rule nor the statute makes clear how the rate of pay’ is to be calculated, or how a bonus is treated for purposes of determining an employee’s rate of pay,— Birkenstock wrote in his letter to the Ethics Committee.

This isn’t the first time the issue has come up. Last year, Senate leadership tried to amend the time period for senior staffers, changing the triggering time from more than 60 days to more than two months, to accommodate months that include 31 days. That would allow bonuses to be paid for at least two months without necessarily triggering the lobbying ban.

Although the bonus provision was passed by unanimous consent, it was part of a bill on staffer paychecks that ultimately did not pass. That legislation has been reintroduced in the House this year.

Still, the junior staffer facing a lobbying ban is rare, according to ethics lawyers.

In fact, staffers considering going to the private sector often consciously adjust their salaries in order to ensure that once they leave Congress they don’t face a lobbying ban.

What may be even more unusual is whether the Senate Ethics Committee would produce interpretive guidance on the issue.

The panel rarely puts out interpretive guidance — the last two times were in 1995 and 2002 — opting instead to give informal opinions on a case-by-case basis.

And it’s unlikely the Ethics Committee will address the issue at large unless there were numerous cases where the bonus triggered a lobbying ban for junior staff, according to ethics lawyers.

“If it was a problem that has been arising with some frequency, then that is when the committee may decide to issue an interpretative ruling,— said Robert Walker, an ethics lawyer at Wiley Rein and former staff director of the Senate Ethics Committee. “This particular issue in my experience has not come up all that frequently in Senate offices,— he added.

The committee has issued an interpretive ruling regarding how bonuses are treated for purposes of filing financial disclosure forms. In those cases, a staffer’s annual salary is determined merely by adding the annual bonus to the annual base pay; there is no extrapolation into a yearly salary when bonuses are paid out over a certain period of time.

Birkenstock would like to see that interpretation put toward the revolving-door provision.

“You should do this in a way that’s rational and has consistent application,— Birkenstock said.