A person identified only by his initials sued the Cherry Creek School District in federal court this week, arguing the district violated his son’s First Amendment rights when it expelled the teenager over an anti-Semitic social media post.

The Cherry Creek High School student, identified only as C.G., posted a picture to Snapchat of three of his friends wearing “silly hats” — including a World War II-era military cap — on Sept. 13, and added the caption “Me and the boys bout to exterminate the Jews,” according to the lawsuit filed Tuesday in U.S. District Court in Denver.

Another teenager saw the post and shared it with her father, who called the Arapahoe County Sheriff’s Office. Police determined C.G. wasn’t planning violence, according to the lawsuit.

“C.G. intended the caption to be humorous; he believed it was so outrageous no one could possibly take his words seriously,” Jamie Hughes Hubbard, one of the family’s attorneys, wrote in the lawsuit.

C.G. initially was suspended for 10 days while district officials investigated the post, then was expelled for one year on Oct. 21, according to the lawsuit.

His father alleged the district didn’t follow proper procedures, and that his behavior didn’t disrupt school operations. He is seeking to force the district to readmit C.G. and remove the expulsion from his records, and has asked the court for compensation for emotional distress and punitive damages.

Representatives from the Cherry Creek School District couldn’t be reached Wednesday due to the Thanksgiving break.

Cherry Creek’s policies allow its schools to suspend or expel students for off-campus behavior if it is “detrimental to the welfare, safety or morals” of other students or staff. Students also can be punished for off-campus bullying.

The lawsuit asserts that public schools can’t punish students for conduct protected by the First Amendment. The issue becomes more complicated, however, when the conduct in question occurred off-campus. Courts in several states have ruled that schools can only punish students for online speech on social media if it substantially disrupts school activities. Most cases have involved disrespectful statements about school officials, so it’s not clear how a court would view a post containing hate speech.