LAST YEAR, the Supreme Court ordered the U.S. Court of Appeals for the 5th Circuit to reconsider the affirmative-action program at the University of Texas at Austin. This month, the appeals court determined again that the university’s admissions policies were constitutional. This was not much of a surprise: The 5th Circuit sided with the university the last time it examined this case. Much less predictable is how the Supreme Court will rule when the dispute comes before the justices for a second time.

We wouldn’t accuse them of having an easy task. Every American should be wary of any instance in which the government distinguishes between people based on race, with bad or good motivations. But in its ruling, the 5th Circuit offered the justices several good reasons to side with the university. Among them: If, as the justices have said, the Constitution can bear public universities instituting some kind of narrow, careful affirmative-action admissions policies, UT Austin’s modest program is a prime example of the sort that should survive judicial scrutiny.

Texas fills most of the seats at its premier public university with students who graduate in the top 10 percent of their high school classes — state policy guarantees them admission. This has had the effect of drawing some students from areas of the state where minorities make up the majority without distinguishing among students based on race. The case is about what the university can do from there. UT fills the rest of its classes with students who get in under a comprehensive, holistic review of their academic and personal records. In that analysis, race can be used as “a factor of a factor of a factor of a factor,” as advocates put it, as admissions officers assemble a complete picture of an applicant’s profile. The 5th Circuit points out that this resembles the sort of individualized review of applicants that the Supreme Court has insisted must occur if race is to be explicitly considered in public university admissions.

The university’s opponents charge that the affirmative-action policy is unnecessary. The top 10 percent program already pulls in minority students. Why do any more?

Among the reasons are the fact that the top 10 percent scheme’s effects on diversity stem from ongoing racial segregation in Texas schools. The scheme also is a blunt tool that overlooks applicants who want to and would contribute to the university. The experience of a minority applicant from a majority minority school, for example, may well be quite different than that of a minority applicant from a majority white school.

Another lesson from the 5th Circuit’s ruling: One reason this and other affirmative-action cases are difficult is that the Supreme Court has not offered public university officials clear guidance on what is constitutionally acceptable. According to the court, public universities, for example, can attempt to achieve a “critical mass” of minority students on campus to expose students to diverse viewpoints and prepare them to participate in a multi-ethnic society. What a “critical mass” looks like, though, is not certain. The Supreme Court should clear up the confusion. In the process, the justices should affirm that UT’s conscientiously designed affirmative-action program, a cautious effort to complement the race-neutral top 10 percent program and seek diversity from a range of student profiles, is permissible.