Yeah, that depends heavily on local ordinances and state law. A friend has been trying to get one for years now.
CO2 is especially important in the first years as you will put new/mixed soil on it - which has a lot of more organic material in it which is now exposed to O2 and will rot - generating CO2. I work in a wine region as a paramedic and we had more than similar cases.
The forgiveness part is not valid for the building authority. They absolutely force people to destroy adjuncts/garden sheds that have 0.3m² than the rule and have been build in the 70ies.