That isn't as good a firewall as one might imagine. Organizations like ALEC push through lots of abusive crap at state and municipal levels. They've got their fingers in hundreds of pies at the same time. If locals aren't paying attention, they can have the laws in force and be on to the next town before anyone realizes what happened.
1) It’s controlled locally, which means it would have to be privatized city by city or county by county.
2) Building code varies by city and county, which makes it much easier for the county to enforce directly.