You are correct. This is complete rubbish & you are not required to obey unlawful ordinances of a local municipality. As to your idea of approaching the City attorney remember this: They are hired & fired at the whim of city officials therefore there is a conflict of interests from the outset on their part & they will always side with their bosses lest being terminated by them. This is also true for Police Chiefs. As you can see the system is stacked against you. I suggest working with sprinklerguy28 & others to coordinate a plan to approach them first with a carrot in hand & if that fails (usually does with these types) then with a large stick (or other household item not covered in their banned items list).
Doesn't this city have many festivals that we could attend in large groups? (Wink, wink).