Same way it does on earth. Whoever actually controls the resource becomes its owner. Once someone establishes an independent presence is space they will claim independence from earth and such treaties and lay claim to anything they can reasonably defend.
shows that if you mine it, you own the ore but not the site. Although you are right that as long as there's no 'space police' there isn't really a way to effectively enforce policy.
Same way it does on earth. Whoever actually controls the resource becomes its owner. Once someone establishes an independent presence is space they will claim independence from earth and such treaties and lay claim to anything they can reasonably defend.