A federal judge has ordered the Labor Department to consider rehiring an alcoholic former employe in a case that may help to clarify the obligations of agencies to workers handicapped by drinking.

In a decision issued last week, U.S. District Court Judge Gerhard A. Gesell ordered Labor to allow George L. Whitlock, who, according to testimony, has been an alcoholic since he was 10, to apply for reinstatement. Whitlock was fired in May 1983 after a 12-week absence.

Whitlock, 56, has been sober for more than a year after undergoing seven months of intensive treatment at St. Elizabeths Hospital, Gesell said. Whitlock, a GS-6 with 23 years of combined federal service, was an administrative supervisor in Labor's solicitor general's office before being fired.

Gesell also said that if a medical exam determines that Whitlock is unfit for future employment, Labor must permit him to apply for a disability retirement -- a step the department had refused.

Whitlock's lawyer, Thomas E. Patton, chairman of the D.C. Bar Association's committee on alcohol abuse, said: "As far as I know, it's the first federal court case to squarely address an agency's responsibility to its alcoholic employes," Patton said.

Gesell's decision said it was "plain that the Department of Labor treated George Whitlock with compassion and tolerance and more patience than many employers . . . . However, it is also apparent that the department fell short of the statutory mandate for accommodating handicapped employes."

When Whitlock started missing work and treatment sessions, Gesell said, Labor was required to give Whitlock a "firm choice" between resuming treatment or facing disciplinary action. Labor did neither, according to the opinion.