Hmmmm, is this illegal?

This is Brentons room, I know that he is 15 years old, but he still loves his monkeys!  He started collecting them when he was 6 years old and had an emergency apendectomy, everyone seemed to get him stuffed monkeys!  Before Bristyn left for college, she "found" this sign at the back of where she works and bought it home.  I noticed it in the back of our truck and I thought that it would look "cool" in Brentons room!  Everyone thinks that it looks awesome, especially Brenton....but are those signs owned by the city???