ONCE AGAIN, home rule -- the hard-won right of Americans living in this capital city to limited local self-government -- is under offensive challenge by outside interests with scant regard for the District of Columbia's electoral process. Thanks to the vigilance of citizens who pay close attention to these affronts, the D.C. Board of Elections and Ethics is looking into a heavily bankrolled attempt by out-of-town gambling interests to put a slot machine proposal on the November ballot. At issue is the way the petition drive was conducted; at stake is the integrity of the city's election laws.

The board, which has been conducting hearings this week, so far has focused on legal procedures for the investigation. The board has issued subpoenas to more than 70 city residents who circulated petitions. They are being summoned to answer allegations that they forged signatures, falsified addresses and committed other violations of election laws. They and others behind the drive have much to explain -- and the board must conduct a vigorous, thorough investigation.

The magnitude of the campaign is unprecedented in the board's history, with 56,044 signatures on 3,867 forms. The board has been reviewing names and addresses. Signatures need to be checked as well. Questions must also be asked of circulators and campaign workers who are alleged to have made false statements about the gambling proposal to get people to sign. Backers of the petition -- and precisely who they all are is not clear -- acknowledge that they imported paid workers from around the country to help circulate petitions and witness signings. How many came and what laws might they have broken? District law requires them to be residents, but former D.C. Council member John Ray, who is serving as general counsel for the slots initiative, argued that the law does not "prohibit nonresidents from participating in the petition process." But to what extent were they "participating"? Submitting a false affidavit is punishable by up to a year in jail or as much as $10,000 in fines.

Two years ago, when a petitions scandal marred the Democratic mayoral primary, the board took action against the forgeries and other irregularities in Mayor Anthony A. Williams's campaign. So must it now enforce the law strictly. The signature-gathering process is a fundamental step in the task of self-governing; when it is abused by paid political operatives it is an affront to all residents of the District.