“Service dogs” at restaurants

The owner at my restaurant has decided they don’t want dogs (inside or out) years after opening. I’ve had a slew of people insisting their dogs are service animals when they clearly are not (dog is yanking on the leash, whining and barking or even jumping(!) at other people and/or does not have a service vest (I know this isn’t a strict requirement). Two days ago I had someone insist their dog was a service dog and hand me a card with the website servicedogcertifications.org that leads to a website that offers to send you a certification for $40.

Is there any recourse for turning away people that doesn’t open me or the restaurant to legal consequences? Or do I just have to deal with servers being snapped at or dogs causing a commotion in the restaurant?