claim of service dog after violating pet clause

[Robert M.]

Slightly high maintenance tenant brought cats into one of my SFHs. My property manager told them not allowed. They said they removed them. Months later a German Shepard is reported there by neighbors ( my best property managers actually). Tenants say they are willing to pay additional rent. First $30 more per month. We refused. next $50 per month. We refused and said no pets. Then $100 more per month. We refused. They said they would board them out. 

Couple weeks later dog is back. We said "no pets" and filed for eviction. They said their sister could no longer keep the dog.

We won the eviction case in front of Justice of the Peace here in Pennsylvania. 

Now they are appealing ( their right) and saying it is a "service dog" for their troubled son ( ADD or ADHD, but not claiming just a JD. 

How should I proceed?  Any suggestions or experiences beating this kind of lying about their "liberal" rights ?

Thanks in advance

bob