Plenty.
Not only does the law require it, so does the Postal Service. Failure to control your pet can result in loss of delivery service!
But more than that: you owe it to yourself, and to your pet, to prevent the pain, lost work time, and general hassle that follows when your dog takes advantage of summer dog days (or any other days) to harm a letter carrier who is trying to perform a service to your household.
Keep your per leashed, fenced, or confined.
Notice 204
April 1996
PSN 7610-01-000-9730