The Live Oak High School students' attorney announced Wednesday that the lawsuit, Dariano v. Morgan Hill Unified School District, had been filed against the district.
The students were sent home by the Live Oak High School principal and vice principal after they were told that wearing American flag clothing on Cinco De Mayo could incite violence. It set off an emotional debate that put Morgan Hill in the national spotlight.
"The U.S. Supreme Court has held for decades that students do not shed their First Amendment rights at the schoolhouse gates," attorney William J. Becker Jr. said in a news release. "Students who wish to show their pride for another nation's heritage should not have their speech protected more than those who celebrate America's."
Becker also said that California law grants students the right to exercise freedom of speech by wearing, "buttons, badges and other insignia."
The lawsuit also names the principal and assistant principal as defendants.
After the incident, the Morgan Hill Unified School District superintendent made it clear the four boys did nothing wrong.
"Regardless of what they were trying to do, and I don't know what they were trying to do, they have the right to wear those shirts on school campus, on all of our campuses and they shouldn't have been asked to take them off," superintendent Wesley Smith said in May.
KSBW.com contributed to this report.