In almost every state in the union there are no laws regulating or licensing dog trainers.
Any bozo can hang out a sign and call themselves a dog trainer.
And a lot of them do. Your job in trying to find a good trainer is to identify and avoid the bozos, and the unqualified trainer who will do more harm than good with your chow. Finding a good trainer is a lot like finding a good doctor or mechanic. Your first impulse is to pick up the phone book and call the nearest one to you. The advantage is that your potential exposure to an incompetent practitioner is limited to one or two visits.