The Obama administration is asking the Supreme Court to reaffirm the right of public universities _ particularly competitive and prestigious ones _ to consider race as a factor in admissions decisions. This welcome and forceful endorsement of affirmative action comes in a friend-of-the-court brief filed by the Justice Department in a case challenging admissions policies at the University of Texas at Austin.

The fact of the administration’s intervention may be more influential than its specific arguments, which reflect the somewhat convoluted reasoning the court has adopted in upholding racial preferences in university admissions. For example, the brief by Solicitor Gen. Donald B. Verrilli Jr. emphasizes that Texas considers race as “one factor among many” in a “holistic” admissions process and does not engage in racial quotas.

True enough, but as the brief also acknowledges, Texas seeks to enroll a “critical mass” of minorities, a process in which “statewide demographics” may be relevant. Critical mass is necessary if African-Americans and other minorities are to be represented in significant numbers in settings, such as university ROTCs, that prepare young people for leadership.

One of the most persuasive arguments for some racial preferences is that the underrepresentation of African-Americans in the ranks of the highest-achieving college applicants is inseparable from this country’s legacy of racial discrimination. Far from offending the 14th Amendment’s guarantee of equal protection of the laws, such policies are consistent with that amendment’s paramount objective of overcoming the effects of slavery.

The problem is that, beginning with the court’s 1978 decision in the Bakke case from California, affirmative action has been based on a different rationale: that including students from different backgrounds enhances everyone’s educational experience.

That “diversity” justification, which looms large in the administration’s brief, is valid as far as it goes. But it gives insufficient weight to the persistent racial disparities in income and education that continue to put minority applicants at a disadvantage.

However it is defended, the constitutionality of affirmative action is the law of the land. The administration’s brief convincingly argues that Texas’ plan satisfies the requirements spelled out by Justice Sandra Day O’Connor in a 2003 ruling upholding an affirmative action plan at the University of Michigan Law School. In that decision, O’Connor wrote that a critical mass of minority students promotes “cross-racial understanding” and helps to break down racial stereotypes.

Since then, O’Connor has been replaced by Justice Samuel A. Alito Jr. Yet an important precedent shouldn’t fall simply because of a personnel change on the court. Chief Justice John G. Roberts Jr. has been skeptica

• Los Angeles Times, MCT Campus