The city of Trenton, New Jersey, passed an ordinance making it unlawful to use any form of sound amplification on the city streets. Keller mounted a speaker on a truck. Through the speaker, he played music and spoke on a microphone while driving on city streets. Keller was convicted and fined $50. He appealed, arguing that the ordinance violated his rights of free speech and free assembly. The city claimed that the ordinance served a legitimate governmental function in keeping the city streets safe and orderly, and did not prohibit or unduly restrict any particular speech. The court probably found that the ordinance was .