Philip B. Heymann, a former professor of Law who left Harvard in 1978 to become assistant attorney general and played a leading role in directing the Justice Department's Abscam investigation, is expected to return here next fall with a joint appointment at the Law School and the Kennedy School of Government.

Although the reinstatement procedure is not yet complete, Law School officials said this week they expect "no problem" in reinstating Heymann, who was forced to resign his professorship last June because of a University rule prohibiting leaves of absence for more than two years.

As head of the Justice Department's criminal division for the last two-and-a-half years, Heymann emphasized controlling white-collar crime.

Although his responsbilities brought him into contact with a wide range of issues--including a new charter for the Federal Bureau of Investigation (FBI), legislation limiting police authority to search newsrooms, and last summer's flap over Billy Carter--Heymann gradually became identified with the undercover operation in which FBI agents posing as Arab sheiks tried to buy favors from U.S. Congressmen.

In a telephone interview last week from his Arlington, Va., home, Heymann strongly defended the Abscam program against allegations of entrapment. Abscam has "undoubtedly had a major effect on corruption all across the country," Heymann said.

"The evidence is all anecdotal," Heymann, who coordinated the investigation with FBI head Clarence Kelly, said. "But you do feel like you're getting somewhere dealing with crooks when an undercover informant tells us that people are afraid to give or take bribes because they're worried that it's part of another Abscam."

Fishing Trip

Responding to criticism that FBI agents used entrapment to lure Congressmen into criminal activity, Heymann pointed to the Justice Department's success in prosecuting officials charged with accepting bribes. Thus far, the investigation has resulted in the convictions of six current or former members of the House of Representatives, and eight others, including the mayor of Camden, Pa., and three Philadelphia city councilors. In addition, former Sen. Harrison J. Williams of New Jersey faces trial on Abscam charges.

Heymann, terming it "a courageous and imaginative investigation that will have a major effect for some time," said Abscam was not initially aimed at Congress. The investigation began as a probe into an art theft, which then grew to cover illegal activities in Atlantic Beach casinos and immigration, he said.

Brownian Motion

"It wasn't a decision to go after politicians... at no time did we sit down and say, let's go after these people," Heymann said. "It moved almost by itself in that direction, and certainly in no way did we discourage it thereafter."

On other matters, Heymann--who led the division which would have responsibility for prosecuting people who failed to comply with draft registration--said he knew of no actions taken by the Justice Department so far to identify or prosecute non-registrants.

Heymann said that in the Billy Carter case--in which the former president's brother was forced to register as a Libyan agent--"we threw our files wide open" and called the matter "a lot of flap over relatively little."

While saying he had no regrets and that "nice progress was made" in controlling both white-collar and street crime, Heymann did say that his successor should "try to bring a little more order and organization among the various departments, agencies and offices involved in federal law enforcement.

Prior to joining the Carter administration in June 1978 at the invitation of former attorney general Benjamin R. Civiletti, Heymann, who is 48, served in the State Department under former president Lyndon B. Johnson. He joined the Harvard faculty in 1969, and later aided Archibald Cox '34 when he served as special prosecutor investigating Watergate