The D.C. Court of Appeals ruled yesterday that the city's elections board may not allow residents with no proof of voter registration to cast regular ballots in Tuesday's election unless the board can prove that this procedure really is necessary.

The court order sent elections officials scurrying to respond and raised the possibility that in Tuesday's general election they may be forced to revert to the procedures used in the Sept. 14 primary, when 22,000 city voters had to cast challenged ballots.

By the end of the day the board had given the court an affidavit saying that, given the chaotic state of current voter rolls, the new balloting procedure is necessary to insure that all registered voters may cast ballots.

David A. Splitt, acting executive director of the board, said in the affidavit that despite recent efforts to correct inaccurate precinct rolls, "I determined there was no assurance that all persons qualified to cast a vote by regular ballot" would be on the new listings.

The court did not make a final ruling yesterday.

The election board's general counsel, William H. Lewis, said that if the court does not accept the board's argument he believes the city will have to return to the voting procedures used in the primary.

At that time, voters whose names were missing from the computer lists had to cast challenged ballots, which were not counted until each voter's registration had been verified by the board. After a month-long certification process, 20,000 of those ballots were counted.

It was in an effort to avoid similar problems that the board decided in this election to allow voters whose names are not on the precinct lists to cast regular ballots if they have a voter registration card or if they sign an affidavit swearing that they are registered.

Elections board chairman Albert J. Beveridge III said that all precinct workers already have been directed to use the new procedure and that if the court does not permit it there could be mass confusion at the polls.

"I really don't know how we can inform all the precinct workers to be sure they know" if the rules are changed, Beveridge said.

The appeals court's three-judge panel issued the ruling in a suit brought by W. Ronald Evans, a Republican candidate for City Council in Ward 5. Evans maintained that the affidavit procedure would leave the election open to voter fraud and amount to "same-day registration," which is prohibited under D.C. law.

His attorney, Melvin Burton, argued that voters who cannot show proof of registration should cast challenged ballots, so that if anyone were found to have voted fraudulently, his vote would not be counted. If regular ballots were cast, they automatically would be counted and later could not be separated from the tally.

The board had argued that it had the authority to institute the new procedure under a D.C. law allowing agencies to make emergency rule changes. In yesterday's opinion, the appeals panel said it was not clear from the board's presentation that the change met that law's requirement of being "necessary for the immediate preservation of the public peace, health, safety, welfare, or morals," and "necessary in the circumstances . . . . "

Splitt said in his affidavit that he had determined that the emergency rule-making procedures were necessary because there was not enough time to follow normal procedures calling for public notification and public hearing before the rules were changed.

In another matter, the appeals court ordered the elections board to notify voters that Council member David A. Clarke (D-Ward 1) is the D.C. Statehood Party candidate for the council chairmanship as well as being the Democratic Party candidate.

The action came as a result of a suit brought by a voter who had written in Clarke's name as a Statehood Party candidate. Clarke ran in the Democratic Party primary, defeating current chairman Arrington L. Dixon and former chairman Sterling Tucker.

Beveridge said that it would be impossible for the board to print and post the required notices in time for Tuesday's election.