Ethically? If you would’ve bought it if you couldn’t pirate it, you should probably buy it.

It would require being couched in some kind of international law, and there really isn’t one that applies to all countries

It’s been tried before, usually as a joke. Kids magazines that say “not for sale to adults”. Gaming mods that make you pledge your first born to the developer. To work, the laws of the country the user is in will apply, and will have to be enforced.