I have been tagged from snakes in their enclosures and outside their enclosures. I think it all boils down to if you snake feels threatened, not necessarily a territorial thing. When you open a snake's enclosure and reach in to grab them all they experience is sudden movement, changes in light and suddenly a big warm thing hovering over them and reaching towards them. I simply open tubs slowly, and if I have a snake that is occasionally aggressive (like my pastel used to be) I would simply tap him gently on his nose with my snake hook and reach right in. You just have to let them know you are not there to hurt them.