In a decision giving sweeping new legal protections to gays and lesbians, a federal appeals court on Tuesday found it as unconstitutional to exclude jurors based on sexual orientation as it is to keep women and minorities off juries.

The 9th U.S. Circuit Court of Appeals found that sexual orientation deserves the strongest anti-discrimination protections in civil rights law, siding with gay rights advocates who argued that gays and lesbians are entitled to the same equal treatment in jury trials as they are in the military, voting and marriage.

The groundbreaking decision underscored the growing importance of recent rulings in gay marriage battles, relying heavily on the Supreme Court’s decision last year striking down a federal ban on same-sex marriage benefits. The 9th Circuit also cited high-court precedents forbidding bias in jury selection based on gender and race.

Bumping prospective jurors from a trial based on sexual orientation continues a “deplorable tradition of treating gays and lesbians as undeserving of participation in our nation’s most cherished rites and rituals,” wrote 9th Circuit Judge Stephen Reinhardt in the three-judge panel’s unanimous ruling. These biases “deprive individuals of the opportunity to participate in perfecting democracy and guarding our ideals of justice on account of a characteristic that has nothing to do with their fitness to serve.”

The decision came in a high-stakes showdown between Abbott Laboratories and SmithKline Beecham, rival pharmaceutical giants that squared off in a 2011 federal antitrust trial in Oakland. The issue arose during jury selection, when SmithKline’s legal team suggested Abbott deliberately removed a juror who was gay because the trial involved a claim that Abbott dramatically jacked up the price of a crucial HIV treatment drug.

Abbott’s drug pricing provoked a furor in the gay community. The company denied ill motives in removing the juror, but the case created a major test of whether a pivotal 1986 U.S. Supreme Court decision in Batson v. Kentucky, barring the exclusion of jurors based on race, applies to gays and lesbians.

The Abbott case also gave lawyers an opportunity to test the scope of the Supreme Court’s ruling last June invalidating the federal Defense of Marriage Act. The 9th Circuit invited the two sides to present arguments on how the marriage ruling applied to the jury issue, and a dozen gay rights organizations jumped into the legal fray to side with SmithKline.

Gay rights advocates argue that equal treatment in jury service is akin to seeking the same rights in the military, voting and marriage. Abbott’s lawyers argued that Supreme Court precedents do not apply to sexual orientation in jury selection and had urged the 9th Circuit to avoid the issue in the antitrust case.

But the 9th Circuit took the issue head-on, perhaps putting the case in a position for eventual Supreme Court review. The panel was decidedly liberal: Reinhardt was joined by other members of the court’s liberal wing, Judge Mary Schroeder, a Carter appointee, and Marsha Berzon, a Clinton appointee.

Legal experts, however, say the Supreme Court may be reluctant to consider this ruling, which could leave a lasting impact in Western states on other cases involving discrimination against gays and lesbians.

Vikram Amar, a UC Davis law professor, said the new legal protection could be particularly important in challenges to bans on gay marriage in other states within the 9th Circuit, such as Nevada, which is defending its law in the same court. California’s gay marriage ban already has been invalidated.

“Today’s ruling will make it exceedingly difficult for states to justify laws that discriminate based on sexual orientation,” said David Codell, litigation director of the National Center for Lesbian Rights.

Meanwhile, as a result of Tuesday’s ruling, the 9th Circuit ordered a new trial in the antitrust feud. A federal jury reached a mixed verdict in the first trial over Abbott and SmithKline’s dispute over licensing agreements and pricing for an Abbott drug called Norvir.

SmithKline said in a statement it was pleased with the ruling, calling it “well reasoned.” An Abbott spokeswoman said the company is reviewing its legal options. The company, which has spun off the division that produces the HIV drug, can ask the 9th Circuit to rehear the case with an 11-judge panel.

Howard Mintz covers legal affairs. Contact him at 408-286-0236 or follow him at Twitter.com/hmintz.