The US Supreme Court announced on Monday that it would not take up a major First Amendment case testing whether school officials in California violated the free speech rights of three high school students who were told they could not wear American flag T-shirts at school because it might upset students of Mexican heritage.

The court took the action in a one-line order. The justices offered no further comment on the case.

A school principal and vice principal at Live Oak High School near San Jose told the three T-shirt wearers that they must either take the shirts off, turn them inside out, or go home.

The administrators said they took the action out of concern that Hispanic students might assault or otherwise harass the students for wearing shirts displaying the American flag on the same day Hispanic students were celebrating Cinco de Mayo at the school.

School officials determined that the threats of violence were credible. Rather than confront those making the threats, the school officials focused on the students displaying the American flag.

The May 5, 2010, incident sparked national headlines – and a lawsuit.

The students charged that school officials violated their First Amendment right to engage in a passive expression of political opinion at their school by wearing American flag shirts.

A federal judge threw the suit out, ruling that school officials “reasonably forecast” that the American flag shirts “could cause a substantial disruption” at the school.

A federal appeals court upheld that decision. A panel of the San Francisco-based Ninth US Circuit Court of Appeals said that in an “era of rampant school violence” involving guns, other weapons, and Internet threats, school officials were entitled to tailor their actions in ways they deemed necessary to avert violence and enhance student safety.

“To require school officials to precisely identify the source of a violent threat before taking readily-available steps to quell the threat would burden officials’ ability to protect the students in their charge,” the appeals court said.

In declining to hear the student’s case, the high court action allows the Ninth Circuit’s decision to stand.

At the center of the case was a 47-year-old free speech landmark decision in which the Supreme Court found a First Amendment right of students at a Des Moines public school to wear black armbands to class to protest the Vietnam War.

The local school board got wind of the planned protest beforehand and passed a resolution banning armbands. The students conducted their protest anyway.

Five were suspended.

They sued. A federal judge ruled for the school district. On appeal, the Supreme Court reversed, declaring that students do not “shed their constitutional rights to freedom of speech or expression at the schoolhouse gate.”

That 1969 decision is Tinker v. Des Moines Independent Community School District.

Lawyers for the American flag-wearing students in California cited the Tinker decision as standing for the proposition that school officials must honor the free speech rights of students who engage in a “silent, passive expression of opinion, unaccompanied by any disorder or disturbance on the part of the [protesting students].”

The flag shirt wearers issued no threats, according to briefs filed in the case. They showed up at school wearing shirts displaying the national symbol of the United States.

In their briefs to the court, lawyers for the school district offered a different reading of the Tinker precedent.

“Tinker empowers schools to regulate student speech that might reasonably [lead] school authorities to forecast substantial disruption of or material interference with school activities,” Oakland lawyer Don Willenburg wrote in his brief urging the high court to reject the students’ case.

He said the authority to restrict student speech is granted to school officials without regard to the source of any substantial disruption. In other words, it doesn’t matter whether the American flag students were well-behaved, silent, and passive. Their speech could be censored if school officials believed their message might provoke a disruptive response from others.

Lawyers for the students said the school district, the federal judge, and the Ninth Circuit had all granted a heckler’s veto to those high school students who threatened violence against the t-shirt wearers.

The episode violates foundational First Amendment principles and teaches a dangerous lesson to public school students, Robert Muise, a lawyer with the Michigan-based American Freedom Law Center, said in his brief on behalf of the students.

“It is far better in our civilized society to teach students about the First Amendment and why we tolerate divergent views than to suppress speech,” Mr. Muise wrote.

“The better and proper response is for school officials to educate the audience rather than silence the speaker,” he said.

He added: “There is never a legitimate basis for banning the display of an American flag on an American public school campus.”

Among those who urged the high court to take up the California case were two of the students who waged the black armband protest a half century ago in Des Moines.

Mary Beth Tinker and her brother, John, were 13- and 15-years-old in December 1965 when they donned armbands to make a point about the Vietnam War.

In a friend-of-the-court brief, they argued that some lower courts have been reluctant to uphold constitutional protections for student political speech at school. Instead, they said, judges often give school administrators broad discretion to censor student speech they find offensive or that they believe might potentially be disruptive.

It is time for the high court to revisit the issue and clarify the core holding in the Tinker case, Washington lawyer Robert Corn-Revere wrote in the Tinker’s brief.

He added that the California case also offered the justices a teaching moment. “This case is about the future of free speech as much as about the present and the past,” Mr. Corn-Revere wrote. “If students learn that threatening speakers is an effective way to suppress speech, this will produce more threats, and more suppression of a wide range of other speech,” he said.

“And beyond this, even peaceful students will learn that free speech must yield whenever its opponents are willing to threaten violence – a message antithetical to all that this Court has tried to convey about the First Amendment,” he wrote.

The case was Dariano v. Morgan Hill Unified School District (14-720).