THANKS in large measure to a lawsuit filed in U.S. District Court earlier this week by the Rev. Jesse Jackson's National Rainbow Coalition and the Citizenship Education Fund, more than 30,000 District residents who were purged by the D.C. Board of Elections and Ethics from the city's voter registration rolls in 1989 and 1990 are expected to be eligible to vote in the September primary and the November general elections. On Thursday, the two groups and the Election Board reached agreement that the local law requiring the purge of nonvoting registered voters from the city's rolls is unconstitutional and an unnecessary procedure. If their agreement is approved at a U.S. District Court hearing on the lawsuit scheduled for next Tuesday, the purged voters will be able to cast their ballots this fall.

This is not the story of an ever vigilant public interest group reining in an inept, indifferent D.C. government agency. The facts are these: under D.C. law, the Board of Elections and Ethics is required to carry out a yearly purge from the register of inaccurate and outdated records. This law requires the board to use the fact of nonvoting during a four-year period as a rule-of-thumb in determining that the voter is not a properly registered District resident. The Board of Elections and Ethics recognized the problems inherent in this procedure some time ago and last December submitted emergency legislation to the D.C. Council trying to get the scheduled January 1990 purge abolished. It described the nonvoting purge as "constitutionally suspect" for punishing voters for the act of not casting a ballot. The council failed to act on the Election Board's legislative request, and Mayor Barry's voice was nowhere to be heard at the time, at least not on this topic.

The Election Board has better ways to maintain accurate and current voting records. Five years ago, it put in place a mail canvass to identify inaccurate and out-of-date voter records. It also worked out data-sharing programs with key city agencies such as Vital Statistics and the D.C. courts and other election boards outside the city to obtain information on registrants who have died or have been jailed as convicted felons or who have moved out of the city and are registered elsewhere. These alternative measures provide some assurance that the integrity of the voting registry will be maintained.

But given the inaction by the council, the lawsuit was a useful goad to ending the old procedure. It, of course, does not automatically follow that an additional 30,000 voters will show up at the precincts on Election Day. Purged voters are the people, after all, who for reasons of their own haven't bothered to vote here for several years despite some very aggressive efforts by the city and other voluntary organizations to ease registration requirements and increase voter turnout. But the fact that another legal impediment to voting will be eliminated is a good thing.