THE SUPREME COURT will consider Wednesday its biggest affirmative action case in a decade when the justices examine the suit of Abigail Fisher, a woman denied admission to the University of Texas (UT) at Austin in 2008. Lawyers for Ms. Fisher, who is white, claim that she suffered unjustly by having to compete against African American and Hispanic applicants in a system that considers race. Ms. Fisher wants the court to deem the university’s inclusion of race in its admissions process unlawful, a request the justices should deny. The worry is that the court will use Ms. Fisher’s case to rewrite decades of precedent, with implications for nearly every campus in the country, public and private.

Nobody should be comfortable with any system that uses race as a criterion to distribute scarce opportunities, such as admission to Texas’s flagship public university. Yet, as Justice Lewis Powell wrote in 1978, the country’s future depends on exposing prospective leaders “to ideas and mores of students as diverse as this nation of many peoples.” So does the legitimacy of institutions such as UT.

In 2003, the last time the justices wrestled with these questions, a narrow majority offered universities a road map for pursuing the “compelling interest” they have in promoting diversity on campus without running afoul of the 14th Amendment, which guarantees equal protection under the law. Universities, the justices ruled, could use race as an explicit factor in admissions in order to establish a “critical mass” of minority students on campus, as long as race was a non-predominant part of individualized assessments. UT’s program is a reasonable effort to follow those instructions, which should not be ripped up after only nine years.

Most of UT’s minority students are admitted under a law that guarantees spots to the top 10 percent of graduating seniors in Texas high schools, a crude system that promotes racial diversity at UT but relies on enduring geographic segregation across the state. For all other applicants, race is “a factor of a factor of a factor,” the university insists, and it is considered only in the context of the rest of their profiles — essays, socioeconomic challenges, extracurricular interests and so forth. The university’s lawyers reasonably argue that the admissions procedures for those outside the 10 percent pool not only increase the number of underrepresented minorities on campus but also introduce needed nuance to the 10 percent law, which can fence out well-qualified individuals who would add diversity between — and within — ethnic groups on campus.

Demand for diversity is widespread because of its many benefits to universities educating students in citizenship as well as calculus, chemistry or Kant. Instead of rewriting the rules, the court should allow the debate about UT’s program, which the university reconsiders every five years, to continue unhindered.