According to Boston’s city ordinances, whenever a dog is off the property of its owner, it’s required to be on a leash. That means that if you’ve been walking through a person’s yard and are attacked by a dog, the dog was likely legally allowed to be off the lead. However, if you were in public and attacked as you walked, then that dog should have been on a leash to prevent injury and to prevent the dog from running away.
Another note about leashing dogs is that if a dog isn’t confined on a property, it must be under control. If the dog is not leaving the boundaries of the yard, then it’s within the rights of the owner to keep it off its leash. If the dog leaves the area and causes trouble to others, then the owner is breaking a law by allowing the dog to roam freely.
The same requirements apply to parks, unless the park has a designated dog-run or dog-park facility. Typically, any family park or public place requires the use of a leash on pets, although a muzzle may not be required.
Source: City of Boston, “City Rules and Regulations,” accessed April. 20, 2015