The American Civil Liberties Union filed a lawsuit Thursday on behalf of a Washington, D.C., man who was arrested after playing “The Imperial March” from Star Wars behind National Guard troops in the district.

Officers of the federalized Metropolitan Police Department arrested 35-year-old Sam O’Hara for playing the song behind Ohio National Guard member Devon Beck in mid-September, according to the complaint. O’Hara followed Beck and recorded him on his cellphone while playing the song in the Logan Circle neighborhood of the district. The MPD officers told him he was detained for “harassing the National Guard,” according to the lawsuit.