The D.C. Court of Appeals has ordered the suspension of Washington lawyer Joel L. Keiler for selecting his boss as the supposedly impartial arbitrator in a labor dispute in which Keiler represented one side.

Keiler, then an attorney with one of the city's largest and best-known law firms, Arent, Fox, Kintner, Plotkin & Kahn, received a 30-day suspension for his part in what the Bar Association's disciplinary board called "a sham arbitration" in which it was "inexcusable" for a lawyer to be involved.

Keiler originally received a private reprimand from the Bar's inquiry committee, but when he appealed that penalty the displinary board recommended the suspension.

Keiler's boss, Allen G. Siegel, who is still a partner in Arent, Fox, Kintner, Plotkin & Kahn, also received a private reprimand. Since he never appealed, his light penalty held and his name would never have publicly connected with the displinary process, had it not been for Keiler's action.

The appeals court, which under District of Columbia law must approve the Bar's disciplinary board recommendations for suspensions, handed down its decision Oct. 17, but did not release it until yesterday.

The suspension took effect Oct. 27 and Keiler, reached yesterday in his Washington office, said he is complying with the court decision and is not practicing law in the District of Columbia. He said he is not appealing the court ruling.

The "sham arbitration" took place in 1971 when Keiler, now in practice for himself, recommended Siegel as the arbitrator in a Miami labor dispute between a Teamsters' local there and the firm's client, Sanitary Linen Service.

According to court records, neither Keiler nor Siegel ever disclosed during the arbitration proceeding - which was won by the linen company - that they were associated in the same law firm.

Moreover, the disciplinary board found that "certain steps were taken to mask the relation between the arbitrator and his law firm." For instance, the board said Siegel signed his name" in a form never utilized by him, as if John F. Kennedy were to have signed J. Fitzgerald Kennedy."

The disciplinary board said Siegel "bears a heavy responsibility for having participated and served as sham arbitrator." The court noted that the two participants received different punishments, but said since Siegel decided to accept the lesser penalty "his case is not before us."