@Hillary54 You can message the guest, saying you are aware that they are disregarding the "dogs on leash only" rule, tell them that they need to comply with this or they will have to leave. If they continue to ignore this, deny it, or send some snotty reply, call Airbnb to cancel the remainder of their booking without penalties to you. They'll be refunded the unused nights and likely leave a bad review, which you can leave a brief response to, making it clear that this guest was disgruntled because they were told to keep their dog on a leash outside, as is clearly stated in your house rules.