REP. CHARLES C. DIGGS JR. (D-Mich.) was convicted last fall of mail fraud and of diverting up to $60,000 of his congressional employees' salaries to pay his personal and congressional bills. And so, to many, a move by the House GOP leaders to expel him from Congress may seem reasonable and required. But the issue is not that easy, and it surely should not be addressed along party lines. The voters in Michigan's 13th District re-elected Mr. Diggs to represent them in Washington, and they did so in full awareness of his conviction. So to expel Mr. Diggs now would be to disenfranchise a group of people who clearly want him in Congress, whatever his condition in the eyes of the law.

Had Mr. Diggs not undergone this test at the polls, there might be a stronger argument for expelling him to allow his constituents an opportunity to vote on whether to send him back to Washington. But given Mr. Diggs's re-election after the fact of his conviction, there is no reason to doubt that, were he expelled now, the voters would return him to Congress yet again.

In any event, expulsion from the House is an extremely harsh action, rarely taken: Only three members of Congress have ever been expelled, and their cases involved treason (because they had joined the Confederacy). The founding fathers did give each house authority to expel its members for gross misconduct, by a two-thirds vote. Though the House has no specific definition of gross misconduct, it should be a narrow one, limited, say, to cases of treason or capital offenses. In other cases, after all, the judicial system would still determine the fates of members convicted of crimes.

There is another point that should not be overlooked in the case of Mr. Diggs. He is appealing his conviction -- and extreme action now could well leave the House in the awkward position of having expelled a member whose conviction is later overturned.

To argue against the expulsion of Mr. Diggs is not to say that the House must honor him with chairmanships and other internal authority to exercise special congressional powers -- some of which he has been convicted of abusing. Having been found to have violated that trust for personal benefit, he should not retain his chairmanships. That is a separate matter. But the Republicans should drop their expulsion attempt.