We agree entirely.

Without the ability to exert control and therefore reinforce the definition, borders are as arbitrary as any other law. They are created by people, enforced by people, and if we change our mind then they can go away. It's not some intrinsic property of the planet.

While I'm ranting, the definition of a relic or artifact is equally arbitrary. As well as the definition of a people. And ownership. At any point in history, these definitions will be different. Right now we've defined it in such a way that we've decided that it is socially acceptable to return relics to people who live inside geographic areas where the relics originated from. This is also arbitrary.

But as long as people, decide to exert force to reinforce this definitions, there is true as any other law.