Several conservative groups and 20 Republican members of Congress have jumped into the legal fray over a South Bay high school's decision to order a group of students wearing American-flag adorned shirts to turn them inside out during a 2010 Cinco de Mayo celebration.

In court papers, the legislators and legal groups urge the 9th U.S. Circuit Court of Appeals to reconsider a February ruling that found Live Oak High School administrators were within their legal rights to act against the flag-wearing students. The groups are siding with the students' families, who have asked the 9th Circuit to rehear the case with an 11-judge panel.

A three-judge 9th Circuit panel previously backed the Morgan Hill Unified School District and Live Oak High administrators, who ordered the students to either cover up the U.S. flag shirts or go home, citing a history of threats and campus strife between Latino and Anglo students that raised fears of violence on the day the school was highlighting Cinco de Mayo.

The school's actions were reasonable given the safety concerns, which outweighed the students' First Amendment claims, the court concluded.

"Our role is not to second-guess the decision to have a Cinco de Mayo celebration or the precautions put in place to avoid violence," 9th Circuit Judge M. Margaret McKeown wrote for the panel. "(The past events) made it reasonable for school officials to proceed as though the threat of a potentially violent disturbance was real."

But the Republican congressional members, the Alliance Defending Freedom and the American Center for Law and Justice in a friend-of-the-court brief filed earlier this month argue the ruling amounts to a "heckler's veto" and violates the students' free speech rights. Steven Palazzo, a Mississippi Republican, and Rob Bishop, a Utah Tea Party member, are the first two legislators listed on the brief.

Lawyers for the students' families have already asked the 9th Circuit to rehear the case, arguing they wore the T-shirts to show their patriotism and did not intend to incite violence with Latino students. They argue there is a broad First Amendment right to show the American flag, regardless of the circumstances and they maintain the school's actions were unconstitutional.

The case is a test of a decades-old U.S. Supreme Court ruling that gives school administrators extensive leeway to take action on campuses when there are legitimate concerns about student safety.

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