Control of borders doesn't imply "everyone keep out." It just means that the government reserves the right to keep people out. Kinda like a trademark, actuall

Control of borders doesn't imply "everyone keep out." It just means that the government reserves the right to keep people out. Kinda like a trademark, actually. One has to "defend" a trademark in order to keep it, which can either take the form of an overeager legal department, or you can just find all the people who are using your trademark and give them explicit permission to do so with the caveat that you may rescind that permission at your discretion (like Hormel did with the word Spam).