He said "Most laws state..." not "Most state's law".
I think a lot of places do have leash laws that require the animal to be contained in some fashion.
I think the dog is probably being protective of it's territory, and is only coming out of the yard on occasion, especially after having "chased" a intruder away. If so, it would be hard to have it picked up as a stray, because by the time the animal control is there, it's back on it's own property.
I personally would attempt talking with the owner in a calm fashion. If they are unwilling to fix the problem in some way, then I would definitely go to the police, or animal control, with video of it's behavior.
Yes, it could be just a big dog who is overly excited, but it still could bite someone, just because it is overly excited and NOT contained. No one wants a child mauled just because it MIGHT not be a problem dog.
I've seen several goldens that were nasty. I saw one that even had 'springer rage' and attacked me with no warning, two seconds after wagging his tail happily. Less than five minutes after the attack, he was wagging his tail again while I bled.
The legal issue will probably hinge on how much OUT of the yard he is, and the video proof of his actual actions.
Good luck.