Mission creep has infiltrated affirmative action.

That’s what I’ve concluded by following Fisher v. University of Texas (UT), the case argued last week before the U.S. Supreme Court. Abigail Fisher, who is white, has challenged UT’s use of racial preferences in undergraduate admissions.

Regardless of the outcome, there are two serious questions just about everyone wants the court to answer. First, when will the need for racial preferences end? And second, how will we know?

Former Associate Justice Sandra Day O’Connor tried to provide some guidance in 2003 with her majority opinion in another racial preference admissions case, Grutter v. Bollinger. In upholding the University of Michigan law school’s right to use race as an admission factor, O’Connor wrote that race neutral standards are clearly the way to go, but determined that preferences will probably be needed for another 25 years or until a “critical mass” of minority students are part of the student body.

Twenty-five years is specific, but what does “critical mass” mean? The late Chief Justice William Rehnquist, in his dissent, lambasted law school officials and the court majority for refusing to define “critical mass.” He predicted future judges would struggle to define it. He was right; that very scenario played out last week.

During oral argument, Chief Justice John Roberts asked UT counsel Gregory G. Garre, “What is that number? What is the critical mass of African-Americans and Hispanics at the university that you are working toward?”

Garre replied, “Your Honor, we don’t have one. And this Court in Grutter…,” Roberts interrupted Garre, saying, “So how are we supposed to tell whether this plan is narrowly tailored (a legal requirement) to that goal?”

Garre said, “To look to the same criteria of this Court in Grutter. This Court in Grutter specifically rejected the notion that you could come up with a fixed percentage.”

In other words, without a definition, critical mass means what the universities say it means. Thus, racial preferences will never go away because race is now the foundation of an ever-widening definition of diversity, which universities more and more claim as fundamental to their mission.

In its brief supporting UT, UNC-Chapel Hill said part of its mission is “to turn a diverse community of students into the next generation of leaders” and flatly stated that it uses race as one of 40 factors for admission.

However, as the U.S. and North Carolina become more diverse, race is an increasingly inaccurate measure. I’d bet low-income white students from rural North Carolina would add much more to the cultural, political and religious diversity of UNC-Chapel Hill than upper-income minority students from Wake or Mecklenburg counties.

What’s more, who decides which race to claim? What is the race of an applicant with white parents, but a minority grandparent or great-grandparent? Universities get around that litmus test by asking students to self identify. But imagine the suspicion cast toward my granddaughters – whose last name is Simpson – should they choose to claim their Mexican heritage on an admissions form. And what is a university to do if it finds its student body has achieved a “critical mass” of diversity but discovers classes are self-segregated by area of study?

No doubt UT and UNC-Chapel Hill will continue to downplay the role of race by noting it is just one factor in a holistic pool of qualifications. Yet, it’s undeniable that race is the defining characteristic in academia’s obsessive pursuit of diversity. Unfortunately, the ever-widening definition of diversity coupled with lack of measurement for “critical mass” has opened to the door to, as Frederick M. Hess wrote in 2003, a never-ending litany of unspoken quotas.

It’s too late to put the diversity genie back in the bottle, but we can give it a deadline. Ending racial preferences of all types by 2028, as O’Connor suggested, should be more than a goal. It should become law.

Sixteen years gives everyone plenty of time.

Contributing columnist Rick Martinez (rickjmartinez2@gmail.com) is news director at WPTF, NC News Network and SGRToday.com. He is also on the Board of Trustees of William Peace University in Raleigh.