The Reagan administration was attacked before the Supreme Court yesterday for putting the auto industry "back in the driver's seat" of safety regulation by repealing the automatic seat belt and air bag requirement for new cars in 1981.

Solicitor General Rex E. Lee, during the same session, told the court that a 1982 appeals court decision reinstating the passive restraint requirement was a "truly startling" action that improperly stripped administrative agencies of their authority to make regulatory decisions.

Once an administration concludes it is "going down the wrong path," Lee said, "it has the authority not to continue down that same path."

The exchange came as the court heard arguments on the most serious legal challenge yet to administration deregulation efforts: A ruling by the Court of Appeals in Washington that the National Highway Traffic Safety Administration and then-secretary of Transportation Drew Lewis overstepped their authority when it rescinded the Carter administration action.

A defeat for the administration could hamper severely its ability, and the ability of all future administrations, to reverse course in regulatory matters after an election, administration lawyers have said.

The dispute stems from a 12-year effort to equip cars with "passive restraints," which supporters and the insurance industry says could save as many as 9,000 lives and $2.4 million each year and prevent 65,000 injuries. The Carter administration regulation would have required that large and mid-size cars built after Sept. 1, 1982, and all cars built after Sept. 1, 1983, include either air bags or automatic seat belts.

While awaiting the effective dates, the auto industry developed automatic seat belts that could be detached by motorists, raising the possibility they would get no greater use than current seat belts. Rather than forbid the detaching belts, however, the Reagan administration withdrew the requirement, saying it had been rendered ineffective by the industry's action.

Consumer groups and the automobile insurance industry successfully challenged the rescission in the U.S. Court of Appeals in Washington.

The standard "had been described as the most important safety regulation on the books," State Farm Insurance lawyer James F. Fitzpatrick told the justices yesterday. It was repealed, he said, with no justification in a way that "shifted back to the industry the authority to meter the pace of safety progress." Under the law, he said, that authority is to be exercised by the agency.

"This doesn't mean an agency can't reverse course," Fitzpatrick said. "But it can't just . . . scrap a regulation" as the administration did.

Justice Byron R. White asked whether a change in views at the top of an administration or a change of administrations wouldn't be sufficient to justify a rule reversal.

"These are not political decisions," Fitzpatrick responded. "These are not questions of changes of administration." He said that whether an administration is "marching up the hill or down the hill," it must "pass muster" under laws mandating adequate justifications for administrative rule changes.

The reversal of the passive restraint requirement was defended yesterday by former Carter White House counsel Lloyd N. Cutler, representing the Motor Vehicle Manufacturers Association, as well as by Lee.