Dogs that can't escape yards can't attack people outside yards. (samthedogtrainer.com)
Dogs that are allowed to roam loose outside the yard may perceive the entire neighborhood as their «territory» and may defend it aggressively. (seaaca.org)
No parks, walks or contact with the ground outside your yard and your house until your puppy is fully vaccinated, that is in about 4 months. (pawsadoptioncenter.org)