[smudgie]

Our little Granddog is a Jack Russel.
You have more chance of being loved to death than ever get bitten by him.

Terriers are known to be territorial and will defend their owners and homes, the dog won’t understand that outside of the gate is not their territory.
A caution to the owner should be suffice if it is the first time the dog has bitten somebody, especially if it was a nip to the ankle.