IT HAS BEEN almost two years since a federal appeals court upheld a ruling that the Norfolk, Va., school district had fulfilled its obligation to desegregate and could set aside a busing plan that had been in force for 14 years, returning to neighborhood schools for young children. Similar reevaluations are going on across the country. A number of courts have found that desegregation has been accomplished and their oversight is no longer needed to correct conditions that existed many years ago. Two important cases have been decided in recent days.

The Oklahoma City school system has been in litigation for decades. In 1972, the U.S. district court ordered the board of education to implement a desegregation plan that involved a great deal of busing. Five years later, the court found that the board had carried out that order and had "slowly and painfully" established a unitary school system. For eight more years, though, the board continued to use the techniques of pairing, clustering and compulsory busing even as the demographics of the school population changed dramatically. Traditionally, black families had lived only in a few census tracts; by 1985, they were spread more evenly across the city. At the same time, the percentage of black students in the system had doubled.

Nevertheless, when the school board proposed a return to neighborhood schools for children in kindergarten through fourth grade, a plaintiff in the original case protested, citing the 1972 order. On Dec. 9, a district court judge formally dissolved that order, ruling that the schools had been desegregated for many years and that a return to neighborhood schools was not an attempt to resegregate. Any future complaints about school discrimination must be brought to court as a new matter, not a violation of the old order.

A similar result was reached by the U.S. court of appeals in a case involving the schools of Austin, Texas. Litigation there had begun in 1970. Ten years later, the school district entered into a consent decree, and for three years the district court supervised extensive busing. The court declared in 1983 that a unitary school system had been achieved, and four years later the school board sought to eliminate busing for children in kindergarten through sixth grade. Here again, the appeals court allowed the change, ruling that the schools were no longer under the supervision of the court by virtue of the consent decree. Any future allegations of discrimination will have to stand on their own.

The problem with these rulings is that they are being made in a vacuum. The Supreme Court has not given guidelines for the termination of desegregation plans. It did say in earlier rulings that desegregation plans are not to be thought of as set in stone, that at some point school districts required to adopt such plans will wipe away the vestiges of past official discrimination and will be entitled to be called unitary and pursue their affairs without reference to a court.

But when? That's the hard part. Those who fought for the plans in the first place fear resegregation if the courts relent. But the courts can't control the schools forever. More and more school districts can be expected in the years ahead to seek a clean slate and the right once again to assign their students as they please. The Supreme Court needs to give better guidance on this subject. Civil rights groups and school boards alike should seek it. Both have a stake in an orderly and reasoned process.