Douglas H. Ginsburg apparently wasn't the only federal employe to get his job without being asked about illegal drug use.

Despite a year-old decision by the Reagan administration to go forward with random drug testing for government workers, federal officials said the government has no standard policy on asking prospective employes about prior drug use.

Job seekers who are questioned about prior drug use -- applicants for law enforcement and other sensitive jobs -- generally are not rejected because of a positive answer as long as the drug use was experimental, infrequent and many years ago.

In about two months, as the result of a decision made before Judge Ginsburg was nominated for the Supreme Court, all presidential appointees and persons seeking security clearances will be asked about prior drug use, said James Lafferty of the Office of Personnel Management. The new policy is expected to take effect when a new questionnaire, an amended Standard Form 86, comes back from the printer.

The new form will ask questions about alcohol abuse and the use of illegal drugs at any time in the previous five years. It will be left to the White House or hiring agency, however, to decide what to do when a potential employe admits previous drug use.

Until now, Lafferty said, the closest political appointees have come to a drug question is a request on a White House form to provide any information that "could be the possible source of embarrassment to you, or to the president, if publicly known."

The question of drug use by government employes was spotlighted by Ginsburg's decision to withdraw his nomination following his disclosure that he used marijuana in the 1960s and 1970s, including a period when he was a professor at Harvard Law School. Since then, members of Congress and presidential candidates have made public statements disclosing their youthful marijuana use.

A survey of major agencies found that most government employes in nonsensitive jobs are never asked whether they've used illegal drugs.

At the Agriculture Department, for example, personnel director Bill Riley said that only 6 percent of the work force -- those employes in "sensitive positions" -- would be subject to questions about drug use. In their cases, he said, the questions would be asked if drug use were revealed during background investigations.

Drug questions are much more common at agencies where law enforcement or national security information is handled, especially when employes must have security clearances.

At the Central Intelligence Agency, Sharon Foster said that previous drug use is considered in employment, but is "not an automatic disqualification." The agency considers which drugs were used, in what quantities and over what time period. Applicants are asked about drug use and are urged "to be honest about it." Answers can be double-checked in the standard polygraph test given to employes before hiring.

"Obviously, if somebody is a drug addict," that applicant wouldn't be hired, Foster said. "And once you join the agency, you can't use drugs. You can't violate the law."

The Defense Department questions job applicants about prior drug use only if they are seeking sensitive jobs with access to national security or fiduciary information, according to spokeswoman Susan Hansen.

The State Department asks prospective employes to provide "specific information" about any past drug use, including the type of drug, frequency of use and how long ago the use was.

At the Justice Department, there is currently no drug question on employment forms that applicants for attorney positions are required to complete, according to department spokesman Terry Eastland. But drug use sometimes comes up in FBI background investigations. If questions about drug or alcohol abuse arise, the prospective employe is questioned about it.

"Drug use is not an absolute ban to employment," Eastland said. "We use a common-sense standard. Typically, if it was just used in high school or college, it's less serious. If it was used in law school or afterward, that's more serious," he said, adding that decisions are made case by case.

Justice Department spokesman Patrick Korten added that it would be unfair to eliminate everyone who's ever tried drugs. "Otherwise, you wouldn't be able to hire anyone below the age of 45."

Eastland said that in fiscal 1986, the Justice Department and U.S. attorneys' offices had 18 cases deemed serious enough for review in which applicants had used drugs including marijuana, cocaine and LSD. He said 16 of the cases arose from the questionnaires that assistant U.S. attorneys are required to complete. He said 11 were hired, six were disapproved and one case is pending.

Stricter rules are used for assistant U.S. attorneys, who are disqualified if they have used drugs since passing the bar exam. For those who admit trying drugs earlier, decisions are made case by case.

Applicants for jobs at the Federal Bureau of Investigation and Drug Enforcement Administration are also questioned about alcohol abuse and prior drug use, and decisions are made on an individual basis.

"It's not a flat no," said DEA spokesman Robert Feldkamp. "If an agent recruit acknowledges having smoked marijuana, we deal with it on a case-by-case basis. If the person was young, in college or in the military, and it was occasional, we'll probably accept him. But if it appears there was a pattern of abuse, he would be disqualified."

The DEA questionnaire requires prospective employes to reveal which drug was used, the circumstances, how often, and the first and last times drugs were used.

At the U.S. Customs Service, spokesman David Hoover said the policy is to ask applicants about drug use. One-time experimentation is not enough to disqualify a job applicant, he said, as long as it occurred at least 10 years earlier.

The Secret Service conducts extensive investigations of all job applicants, including questions about prior drug use. For agents who carry guns, a polygraph test is given in which agents are asked if they have been truthful in prior parts of their background investigation.

At least one agency may tighten its rules. William S. Sessions, new director of the FBI, has made it clear that he may consider imposing tougher hiring regulations for persons who have tried drugs. "I do not want FBI agents who have violated the law by using drugs . . . . It is not decriminalized, and I hope it is not decriminalized" in the future, he said.