So let me get this right.....AAV's are illegal.... but HD sells them anyway....a homeowner buys some and you point him out to some inspector who asks you who you were talking to. The inspector leaves with the homeowner to make him do what? Inpsect what he is doing and fine him? How about the inspector goes to the HD manager and tells him to remove the illegal devices and writes them a fine for selling illegal devices. Sounds rediculous to me to focus on a homeowner. It also sounds rediculous to me that AAV's are ok in some places but not in others or that some things are OK someplaces but not others....the entire code and inspection process is somewhat ambiguous since it varies everywhere you go.......Makes ZERO sense to me.
Rich sadly we can not stop places from selling items that do not meet the plumbing codes. Even the local plumbing supplies carry items that do not meet the plumbing code. That is why it is up to a Licensed Plumber to know the plumbing codes and to plumb things properly. The inspector is not going to fine the guy as long as he pulled a permit and has a Licensed Plumber doing the work. If not the fines will be stiff. A fine for making plumbing modifications with out a permit, and doing plumbing without a license.
I have seem plumbing, building, and code enforcement officers camping out the Lowe's, Home Depot, and such and follow contractors, home owners back to their home to see if they have a permit for the kind of work they bought the material for. I have had a plumbing inspector follow me to a job site after leaving the Depot with 30 foot of Type L 1" copper. When he seen I pulled up on the job site he showed me his license and then asked to see mine, then asked to see the permit for the job, which I had since I was repiping some meters in a meter room. I never get angery with an inspector doing his job.
One of the things I learned the hard way is to call the local building department and ask for a list of what I need to get permits on. Some towns/cities want a permit to just test and RPZ, or change a water heater. We are a nation of rules, we need to follow the rules no matter how much we disagree.