The golden rule of dealing with service animals is never to touch or distract them.
When you interact with a service dog unsolicitedly, you're potentially putting its handler in danger as the interaction can interfere with the dog's ability to focus on its tasks. So, keep your hands to yourself and focus on the job!
Source: Paws of War, 2018.
Photo by Ralph (Ravi) Kayden on Unsplash.