The ADA does not regulate service dog trainers at the federal level but instead leaves it up to each state to regulate through their business license. Each state has the power to define who a trainer is through their business and professional occupation licences. CA actually regulates guide dog trainers, the same as doctors or engineers, before a professional board. Owner-Trainer friendly states are just states that didn’t define who is allowed to train, or set any requirements. The original intent of the ADA was “if you had the ability or facilities to train your own dog, you could.” somewhere along the line, it became anyone qualified or not could train. (Imagine if everyone was allowed to learn to drive on the open roads, no test, no government intervention, just like 100 years ago with horse drawn wagons.)
Every professional service dog trainer and/or organization that is a member must be properly registered/licensed in their state and authorized to train service dogs under their state law. This elminates the handman type trainer who is a friend of friend who may have very little knowlege of service dogs, their laws or ediquite.
For owner-trainers to become members they need to be connected to a member school who can oversee the dogs training and help guide the process and ensure the standards are being adheared to.