There Are No Regulations
Anyone can call themselves a Behaviourist, Behaviour Specialist, Behaviour Expert/Consultant, Dog Trainer, etc
There are zero regulations in place to protect consumers from unqualified "pet professionals" claiming they will fix your dog
Be wary of anyone that claims they will "fix" your dog, or uses tools such as ecollars or approaches to changing behaviour that is intimidating and coercive.
Walk away. Even if you've spent money! If something feels off then do not continue to work with that person, your dogs welfare is at risk.
Considerations
Avoid hiring anyone that does not have qualifications and continuing education listed on their website. They should make it clear that they use or do not use specific methods and tools. Transparency is key.
Checklist for choosing a trainer
The American Veterinary Society of Animal Behaviour: Choosing a Trainer
TV Dog Training Shows
What Is Wrong With the Dominance Theory?
What Science Says About Shock
Dog Training Myths
Types of Professionals
Trainer: Typically work on manners, learning new skills, etc. Many also address basic behaviour concerns such as house training or unwanted chewing
Behaviour Consultant: Typically educated in behaviour modification and learning theory Modify existing, unwanted behaviours. Some are also trainers.
Veterinary Behaviourist: Vets who have completed residency or training in behavioral medicine. Can work directly with your vet or directly with you if available and can determine when behaviour medications should be applied and which ones are appropriate.