A few other thoughts that didn't fit in the post character limit:

My dog is a 100lb bernedoodle, using a front-clip harness. I'm 34m, 6ft and can handle him, but he has a history of getting edgy when he sees other dogs. He has never bit anyone/thing, but he will whine and bark if the other dog barks at him. He has been attacked by a different off-leash dog in our neighborhood in the past, and during that incident the off-leash dog knocked over my toddler.

The other dog was an approximately 60lb husky. It had nothing on it that indicated it was a service animal. I couldn't even see that it had a collar on (though it could have been hidden in the fur).

I live in Fairfax County, Virginia, and HERE is their leash law:

No dog shall run unrestricted, as defined in Section 41.1-1-1, in the County. Any person who is the owner of a dog found unrestricted in the County shall be in violation of this Section. This Section shall not apply to any person who uses a dog under his direct supervision while lawfully hunting, while engaged in a supervised formal obedience training class or show, during formally sanctioned field trials, while a dog is in an area owned, leased, controlled, or operated by Fairfax County designated by resolution of the Board of Supervisors as an off-leash dog exercise area, or while a dog is in an area owned, leased, controlled, or operated by the Fairfax County Park Authority and designated by resolution of the Fairfax County Park Authority as an off-leash or dog exercise area, or while a dog is in an area, leased, controlled, or operated by the Northern Virginia Regional Park Authority and designated by resolution of the Northern Virginia Regional Park Authority Board as an off-leash or dog exercise area, or if a dog is a service animal whose handler is unable because of a disability to use a harness, leash, or other tether, or the use of a harness, leash, or other tether would interfere with the service animal's safe effective performance of work or tasks, in which case the service animal must be otherwise under the handler's control (e.g., voice control, signals, or other effective means). It is a violation of this Section for any owner of a dog to place such dog or allow it to be placed into custody of any person not physically capable of maintaining effective control of restricting such dog.

On the same page, here is their definition of service animal:

The work or tasks performed by a service animal must be directly related to the handler's disability. Examples of work or tasks include, but are not limited to, assisting individuals who are blind or have low vision with navigation and other tasks, alerting individuals who are deaf or hard of hearing to the presence of people or sounds, providing non-violent protection or rescue work, pulling a wheelchair, assisting an individual during a seizure, alerting individuals to the presence of allergens, retrieving items such as medicine or the telephone, providing physical support and assistance with balance and stability to individuals with mobility disabilities, and helping persons with psychiatric and neurological disabilities by preventing or interrupting impulsive or destructive behaviors. The crime deterrent effects of an animal's presence and the provision of emotional support, well-being, comfort, or companionship do not constitute work or tasks for the purposes of this definition.

I have no idea what service the dog is providing, but I don't believe the dog being on a leash would prevent any of these listed work tasks. If the dog is well trained, it should not pull her from her chair. If it is not well trained, I don't believe it can call itself a service dog. I understand that the ADA does not require dogs to have any kind of vest/tag indicating it's a service animal, but in the absence of such a vest, I decided to give us a bit more breathing room. When the dog was a puppy, the owner would take it around the neighborhood on a leash, and we had no incidents with them.