Affirmative action proponents took a hit Monday as a federal appeals court panel upheld California's ban on using race, ethnicity and gender in admitting students to public colleges and universities.

The ruling marked the second time the 9th U.S. Circuit Court of Appeals turned back a challenge to the state's landmark voter initiative, Proposition 209, which was passed in 1996.

Affirmative action proponents, who had requested that the court reconsider its 1997 decision after the U.S. Supreme Court ruled in 2003 that affirmative action could be used in college admissions, said they would continue fighting.

"We think the decision is wrong," said Detroit attorney George B. Washington, who is representing the group of minority students and advocacy groups that filed the latest challenge in January 2010.

Washington said he would ask the full appellate court to review the case since this decision was issued by a three-judge panel.

In its ruling, the court rejected the plaintiffs' arguments that a new ruling is needed and said the previous decision still applies.

Ralph Kasarda, attorney with the Pacific Legal Foundation who had argued in favor of the ban, said the court's decision was not surprising since the issue had already been decided. This case was redundant and baseless, he said.

"The bottom line from both decisions by the 9th Circuit -- today's and the ruling 15 years ago -- is that California voters have every right to prohibit government from color-coding people and playing favorites based on individuals' sex or skin color," Kasarda said in a statement.

At least six states have adopted bans on using affirmative action in state college admissions. Besides California and Michigan, they include Arizona, Nebraska, Oklahoma, and Washington.

Advocates of affirmative action say such bans lead to the exclusion of minority students and less campus diversity.

In California, the year after ban was adopted, the number of black, Latino and Native American students at the University of California's most prestigious campuses -- Berkeley and Los Angeles -- plummeted by 50 percent, according to the plaintiffs cited in the court opinion.

The university has tried to compensate for the drop in those students by using other admissions criteria, including a "comprehensive review" of applicants, admitting the top 4 percent of graduates from any high school and decreasing the weight of standardized tests, the opinion said.

But affirmative action proponents say the measures have not been enough to boost opportunities for historically excluded minorities.

Although blacks, Latinos and Native Americans comprise about half of California's high school graduates, they make up only 19.5 percent of the current freshman class at UC Berkeley. Whites compose roughly 30 percent and Asians 48 percent. The remainder is out-of-state students.

Backers of affirmative action bans say ruling out race, gender and ethnicity criteria guarantees that all applicants are treated fairly and not discriminated against.

The issue has led to protracted legal battles in several states.

In 2003, the U.S. Supreme Court said the University of Michigan Law School could consider race in admissions decisions to promote campus diversity.

That decision led to a three-judge panel of the U.S. 6th Circuit Court of Appeals overturning Michigan's affirmative action ban last year. The full appellate court, however, has agreed to reconsider the case.

In February, the U.S. Supreme Court agreed to hear another case against the University of Texas, alleging that use of affirmative action is discriminatory. If the court decides against the university, the ruling could definitively end consideration of race in public university admissions.