Mrs Dan had a Malamute before we were married. One hundred twenty pounds of barely domesticated fiercely protective canine.
It was in the back of her pickup properly restrained and a smaller dog jumped in and attacked it. Big Vet bill for the owner of the smaller dog.
We used to live in a very rural place where there was no leash law, but if your dog chased deer or livestock it could be shot and tough luck for you and the dog.
We were a couple of miles from the nearest paved road and we had a dalmatian who would chase us for at least a mile at 25 MPH before he gave up or we took him back to the house and restrained him.
He had been kicked real hard by one of our animals and never chased livestock, but our cars were fair game. We had to restrain him whenever we went somewhere.
Well, today I was cruising through the corn, bean, and beet fields that line the roads in Minnesota near me and a smaller Keeshond gave chase.
I saw it and stopped, becoming the aggressor. Mr. Brilliant, the owner of said dog, said "just ignore him"... Fortunately for the dog, it ran away when I went after it with the front wheel. The next level would have been the Silca Tatico pump I always carry.
So, yeah, restrain your<deleted> dog.