President Carter, whether he realizes it or not, has hired as his chief civil rights enforces some of the nation's most outspoken advocates of school busing.

But Carter the candidate campaigned against busing - and how hard the onetime desegregation warriors in his administration will be allowed to press for school desegregation is now anyone's guess.

So far the record is murky. Two legal briefs the administration has filed since January appear to advocate widespread busing, but Justice Department officials insist they don't depart from basic policy set under President Ford. One brief downgrades busing. And the administration's first move to use the other tool available - administrative enforcement - has become mired in controversy on Capitol Hill.

"They talk a much better game over there, but so far it isn't clear if they'll play a better game," observed Joseph Rauh Jr., one of their former allies on the desegregation front. "You figure such good people should do better things. They'll be better than the last crowd, but they haven't shown what you'd expect from an administration elected by blacks."

Consider the Carter civil rights enforcement lineup. It reads like a "Who's Who" of the under-40 crowd of the school desegregation movement.

At the head of the Civil Rights Division in the Justice Department is Drew S. Days III, who as an outsider argued some of Florida's most controversial desegregation suits during the last seven years. Days' old colleague at the NAACP Legal Defense Fund, Norman Chachkin, is now assistant director of policy and planning in the Office of Civil Rights of the Department of Health, Education and Welfare.

The director of that office is David S. Tatel, another young civil rights lawyer whose best-known suit enjoined Port Gibson, Miss., merchants from collecting a $1.2 million civil damages award from the NAACP in a boycott case. Tatel's top deputy for enforcement is Cynthia Brown, another veteran school desegregation shock trooper, who has worked with the Lawyers Committee for Civil Rights Under Law and the Children's Defense Fund.

The new enforcers took their Carter's administration jobs with mixed feelings and strong beliefs. "It should make an enormous policy difference to have people in those positions," said Jack Greenberg, director of the Legal Defense Fund. "I know Drew Days. He worked in this office and has a real commitment to school desegregation. I know Norm Chachkin . . . I know he hasn't suddenly changed his philosophy just because he's gone to the other side."

But it's hard to chart any drastic new movement on the school desegregation front during the last five months. And if the Carter administration has an overall school desegregation policy, it isn't discernible. For once in office the desegregation warrious lowered their voices and moved cautiously, hamstung by the very bureaucracy they failed against a few months ago.

At the Justice Department, Days, the first black assistant attorney general to head a major division, leans back in the office J. Edgar Hoover once occupied. The administration, he says, is committed to school desegregation "in the most effective way possible, but we believe conflict can be kept to a minimum . . . If there's a distinction to the administration, I believe it's that we're made sensitive and sophisticated in dealing with the issue."

At HEW, David Tatel, 35, says he has spent most of his six weeks in government reorganizing his office, which he claims was left in disarray by the Ford administration. "I was never aware how much longer it takes to get things done in government," he says. "The fact that we haven't accomplished school desegregation in six weeks doesn't mean we're not committed to it."

The history of school desegregation is checkered. Nobody really talks about it - neither the Democrats nor the Republicans like to admit it for their own political purposes - but more school integration took place during Richard M. Nixon's first term than any period since the 1954 landmark U.S. Supreme Court decision.

In 1968, when Lyndon B. Johnson announced he would leave office, 68 per cent of the nation's black students went to schools that were 80 per cent or more black; 2.5 million of them to schools that were all black. By 1972, when Nixon was running for re-election, 45.2 per cent (a percentage that hasn't changed significantly since) were going to schools that were 80 per cent black, and fewer than a million went to all black schools.

It was during these years that desegregation become more a northern and western problem than a southern one. And today the real desegregation battleground is in the nation's large cities - particularly in the Northeast and Midwest - with their growing black enrollments. In 1974, the last year for which statistics are available, 75 per cent of the black students in the nation's largest cities attended racially isolated schools.

In New York City, 33 per cent of the minority students that year had no white classmates. The figure in Chicago was 79 per cent; in Philadelphia 56 per cent; in Detroit 49 per cent; and in Washington, D.C., 85 per cent.

There is no clear sign on how the Carter administration intends to deal with big-city segregation or busing. The Ford and Nixon administrations tried, with only mixed success, to restrict mandatory busing, and let courts - rather than HEW - enforce desegregation laws, a policy that led U.S. District Court Judge John H. Pratt to rule in 1973 that HEW "has not properly fullfilled its obligations to eliminate school segregation.

As a candidate, Carter opposed mandatory busing and as governor of Georgia he once advocated a constitutional amendment against busing (a stand later reversed). But his administration's only policy shift on the issue appears to commit it to a more aggressive use of busing.

That shift was a decision by HEW Secretary Joseph A. Califano Jr., with approval of the Justice Department, that it was legal for the government to cut off federal funds from school districts that refuse to merge black and white schools to solve segregation problems. It would enable HEW to force Kansas City, Mo., and other school systems to use two desegregation techniques, called "clustering" and "pairing," which normally require some busing. But by doing so the Califano "paring" policy would have skirted a congressional limitation set in an amendment sponsored by Sen. Robert C. Byrd (D-W.Va.) in 1974.

The Califano decision boomeranged. Desegregation forces, who consider the Byrd amendment unconstitutional, said the new policy didn't go far enough and that if the administration was serious on the issue it would lobby to have the Byrd amendment removed from the law, which it didn't. Antibusing forces said Califano went too far and his new policy was based on questionable verbal footwork. Last Thursday, the House approved an amendment, 225 to 157, designed to block the Califano policy.

"That hurt us," Tatel said. "What the amendment does it limit our ability to eliminate vestiges of past dual systems or past acts of discrimination. We'll be prevented from any significant enforcement of Title VI of the 1964 Civil Rights Act in the North and West unless it's declared unconstitutional."

If there's been any policy shift in the courtroom, it's been a gradual one. Issues appear to be being handled on a case-by-case basis. The Justice Department, for instance, opposed a busing plan between city and suburbs in Indianapolis a week after it had endorsed a busing plan for Wilmington, Del., between city and suburbs.

William L. Taylor, director of the Center for National Policy Review at Catholic University Law School, said he senses an emerging legal stance which may prove more fair to desegregation advocates. "The last administration was really trying to cut back," he said. "We've now moved into a period when the active opposition of the government has ceased."

But Taylor and other desegregation advocates say the administration has yet to face the tough school issues: what role HEW will take in solving segregation problems (its powers under the Byrd amendment are limited); what its position will be on cross-district busing, and how much resources and technical advice it wants to commit to helping local school districts deal with segregation problems.

Both Day and Tatel, the administration's two enforcement chiefs, make it clear in interviews that they see mandatory busing and metropolitanwide desegregation as necessary to correct past segregation practices in some cases.

But how will this square with President Carter?

"I don't know," answered Days. "You'll have to ask him about that." Tatel said he didn't know what Carter's campaign stands on the issues were. "We're operating on the assumption here that our purpose is to enforce Title VI of the 1964 Civil Rights Act."