I think a strict public access test would be more than fair. That would at least end of the problem of "service dogs" attacking/barking/being a nuisance in public.
It would not end it.
The problem with faker service dogs has absolutely nothing to do with training, with service dogs, with people, with rights, with anything at all in the whole world.
The only problem with faker service dogs is ignorance.
Despite many training classes to businesses, and businesses being told repeatedly their rights when it comes to service dogs, people are still ignorant and don't know the very basics of their rights and what they can or can not do.
There would be a lot less fakers if businesses took the time to teach people how to enforce the already existing laws.
Don't punish the disabled because the abled are ignorant.
If you require certification for service dogs, this is what *will* happen:
Businesses will STILL be ignorant. Faker SD's will be able to show anything they want to a business and be given access, because people won't know what a real certification is supposed to look like.
People will STILL be able to buy certificates for fake SD's because they don't know the difference between a legitimate place and a scam website.
Certification solves nothing. It punishes the people who are honest, and does nothing for the people who are dishonest.
If you want to stop fakers, then stop ignorance. Teach people how to enforce ALREADY EXISTING laws that protect them from faker SD's.