White House counsel Fred F. Fielding found "nothing per se illegal or unethical" about the purchase of nine luxury automobiles by White House deputy chief of staff Michael K. Deaver and some associates on an official trip, but Fielding ordered the rules changed to prevent it from happening again, it was announced yesterday.

Presidential spokesman Larry Speakes said Fielding had completed his inquiry into the discounts received by Deaver and others holding diplomatic passports who bought the BMW autos in Munich while traveling to prepare for Reagan's trip to West Germany in May.

Speakes said Fielding found the cars were bought by four White House staff members, including Deaver; two Secret Service agents and three U.S. Embassy personnel. None of the others were identified. Previously, a spokesman for the Secret Service had denied that any agents had purchased cars.

Speakes said the Secret Service agents had canceled their contracts because the purchases violated agency rules.

He said that none of the four White House staff members who purchased the cars intended to resell them for a quick profit, and that anyone who did would be dismissed.

There have been reports that the cars were purchased at discounts from 15 percent to 25 percent.

Speakes did not make public written results of Fielding's inquiry. He announced, however, that the counsel had issued a memo to staff members outlining guidelines for such purchases in the future.

Among the new rules, Speakes said, is one requiring that any White House official who receives such a discount must be out of the United States for at least 30 days. Previously, this did not apply, Speakes said, adding that Deaver was away for about 10 days.

Deaver led a White House advance party that was making plans for Reagan's visit to West Germany, Spain, Portugal and France in early May.

Speakes said Fielding found that such purchases were a "longstanding practice."

Speakes also said Fielding had determined that the discounts received by Deaver and the others were not regarded as gifts as long as they were available to all government employes or to a special group. In addition, Speakes said, the counsel advised White House staff members not to take such discounts from firms that do business with the White House.

He indicated that such a restriction also may apply to firms that would be influenced by White House policy decisions, such as import tariffs.

According to U.S. News & World Report magazine, Deaver had his car built to U.S. specifications. The magazine said many Americans who purchase autos in Europe that are built for European customers run into a tangle of U.S. rules requiring bringing the vehicles into line with safety and emission standards