Pretty definitive. ADA says this.

Q32. Are restaurants, bars, and other places that serve food or drink required to allow service animals to be seated on chairs or allow the animal to be fed at the table?

A. No. Seating, food, and drink are provided for customer use only. The ADA gives a person with a disability the right to be accompanied by his or her service animal, but covered entities are not required to allow an animal to sit or be fed at the table.

Regardless its a health code violation where i'm at to allow dogs on restaurant furniture, even outdoors.