I'm not sure I understand the question. Well, if they're constitutionally incapable of obeying the law, that's kind of beside the point. It's similar to the animal rights question.
Animals have no conscience, neither do vampires.
Therefore, neither can obey laws or make contracts. No, that's the trick. And their good behavior stops as soon as it's not in their interests to conform any longer. They're basically well-behaved sociopaths. If you are a Free-Market.