Asserting that Sterling Tucker has been so more than a "de facto" chairman of the D.C. City Council for the past three years, Corporation Counsel John R. Risher Jr. made his final appeal to the Superior Court yesterday to oust Tucker from office for alleged violations of the home rule charter.

"If the facts are undisputed, the law is automatic. What room is there for discretion?" Risher told Chief Judge Harold H. Greene in oral arguments observed by a small crowd of fewer than two-dozen spectators.

While maintaining the innoecnce of his client, Tucker's lawyer asserted in response that even if Tucker had inadvertertly violated charter restrictions on outside income by working as a lecturer at Howard University, removed from office was too harsh a punishment.

"Throwing the chairman of the Council out of office at this late date would send shock waves throughout this community," said Harley J. Daniels. "Chairman Tucker holds good title to his office."

The 2 1/2 hours of oral arguments signaled the approaching end of one of the most controversial and politically shadowed law cases in the past three years of limited home rule. The controversy began in June when Risher first asked for Tucker's removal from office.

Risher, the city's chief layer and a close confidant of Mayor Walter E. Washington, contended that Tucker had violated the charter by working for two years as a lecturer and instructor at Howard. The charter requires the Council chairman to work full-time for the city and not hold any other salaried job.

Tucker contended that his employment at Howard, for which he was paid $18,000, was exempted from the provision and asserted that he in no way tried to hide the work because he routinely reported the income from Howard to the D.C. Board of Elections and Ethics.

Neither side is disputing the facts of the case, which have been detailed in court papers filed before yesterday. What is in dispute, however, is whether Tucker's work was illegal and if so whether he should - or must - be removed from office.

Judge Greene did not say yesterday when he would rule, though some persons familiar with the case said a decision could come within two weeks.

Early in the arguments, the judge asked very pointed questions of Risher, trying to pin down whether the entire legal action is meaningless because it was filed June 6, a week after Tucker quit the job at Howard.

Risher said the time of the filing was not that important, because not holding an outside job is a requirement for maintaining office. Tucker forfeited his right to hold office on Jan. 2, 1974 - the day he was sworn - by continuing to work at the university, Risher argued.

The judge also pressed both lawyers on their interpretations of the meaning of an outside position. Risher said that the ban applied to any outside employment "for profit," while Daniels argued that the limitation was only on a position that would detract from Tucker's ability to work fulltime for the Council.