Just found a potential way to circumvent the "You can't do that here" block on opening containers in foreign tribal territory if they are right on the edge of the territory. If you right click a container to open the interaction dialogue and click "open" or "pick up" it will say "You can't do that here." However, if you right click and then back up so that you're no longer in tribal territory, THEN click "open" or "pick up" it will let you do it. If you try and move or discard any items from the container while you're outside the territory zone that it's in, it will automatically close; however, once you have the container opened, you can step back into the territory and it will allow you to take whatever you want normally.