A service dog should be trained and certified. I'm not sure how this would be done--locally or nationally, but there needs to be some standard, some minimum requirement.
Maybe a federal form at the airport, the owner certifying under penalty of perjury that their dog is a trained and real service dog, then prosecuting a few people as examples for violating this?
I agree. These people are cut from the same cloth as those who use fake or “borrowed” placards to park in the handicap spots. There needs to be, I hate to say it, regulation of service animals, and significant penalties for those who abuse it.