That is what I was trying to point out. Hence asking those who claim there is a law to be specific and give us which one and what it says. Interestingly they either don't answer or are vague in their answers. If there was such a law it shouldn't be that hard to point it out.
Agree. Lot of false mystique goes on.
I worked for a year VIP'ing tanks at a dive store, but I have never received any formal training beyond guidance from other store employees. The most complex part was how to punch the dates on the stickers without ending up with some kind of tear. I still VIP my own tanks except for my doubles which are a pain in the @ss to VIP.
Bizarrely, I am actually certified to O2 clean tanks, although I have never actually done one since the training course.
Although probably not for the reasons he implied though, rigdiver might be right - putting a label on an item which falsely indicates some form of testing or inspection can constitute the criminal offence of forgery in many jurisdictions. But if you are satisfied in your own mind that your tank is O2 clean and you are not planning to fill it with 40+%, I personally wouldn't have too many reservations about circumventing the gougers.