The Reagan administration's top civil rights enforcer took his anti-busing policy message to Capitol Hill for the first time yesterday, but declined to endorse a Senate bill to strip lower federal courts of jurisdiction in such cases.

Assistant Attorney General William Bradford Reynolds told the Senate Judiciary subcommittee on separation of powers that the Justice Department has not determined the constitutionality of the bill sponsored by Sen. John P. East (R-N.C.). Generally, he said, bills limiting busing "reflect the thinking of the administration."

Reynolds cautioned that the bill was so broadly drafted that it also banned use of school closings and teacher transfers, other desegregation remedies the department has proposed advocating as a substitute for busing.

Sen. Howell T. Heflin (D-Ala.) said East's bill was "10 years late" and "anti-South" because it would prevent southern school districts from seeking to modify existing busing orders for other remedies.

In articulating new policy on school cases, Reynolds said he would ignore the Supreme Court's 1973 decision in a Denver school case that said racial imbalance in one part of a school system would be considered state-imposed if there was a such a finding elsewhere in the system.

Instead, he said, the department will seek to limit the remedy only to those schools where racial imbalance is caused by state action.

Another witness, Thomas I. Atkins, general counsel of the NAACP, said after the hearing that Reynolds' policy is "disastrous." "If they persist, it is likely we will sue the Justice Department for failing to enforce the civil rights law," he said.

One of the most recent incidents that concerns civil rights advocates is disclosure of a memo sent by White House political affairs aide Lyn Nofziger to Reynolds, his Justice superiors and White House counselor Edwin Meese III in August just before the department reversed its position in a busing case in Seattle.

In the memo, Nofziger urged a "careful look" at the Washington state attorney general's position that the state law banning busing was constitutional. "Not surprisingly, he, like 99.9 percent of the people who have supported Ronald Reagan in the past, is at odds with mandatory school busing--as I think we all are," Nofziger wrote.

"Surely, if we are going to change the direction of this country, mandatory school busing is a good place to make changes--as I thought we would do because I thought that was what the president wanted," he wrote.

Reynolds said after the hearing that he does not consider the memo a form of White House pressure.

Both East and Sen. Jesse Helms (R-N.C.) cited public opposition to busing. Helms also read an exhaustive list of gallons of gas consumed and miles traveled by North Carolina schoolchildren being bused, but did not say how many were being bused for desegregation purposes.

East scolded U.S. District Court Judge James B. McMillan, who ordered busing in Charlotte, N.C., in 1970, saying at one point that "you can't expect people to obey orders simply because they are handed down by federal judges."

McMillan told Sen. Max Baucus (D-Mont.) that judges sometimes are forced to order busing because "we can't go by public opinion. That's the problem with Sen. East."