All the time, everywhere.
No, seriously. Don't Move Firewood isn't about a place, or a bug, or a tree in particular. It isn't even about a given ecosystem. Heck- it is not even about native trees. It is about human behavior.
Do you cover your mouth when you sneeze, even if you don't think you have a cold? Sure you do- it is the right thing to do. Likewise, it doesn't matter if you think that your firewood is probably free of forest pests. You still shouldn't move it very far.