Legal positivism and deontic detachment

I consider a puzzle that arises when the logical principle known as “deontic detachment” is applied to the law. It is not possible to accept the principle of deontic detachment in a legal setting while also accepting that the so-called “social facts thesis” applies to all legal propositions. According to the social facts thesis, the existence and content of law is determined by the attitudes or practices of legal officials. Abandoning deontic detachment is not an appropriate solution to the problem—the puzzle can be recreated with other plausible closure principles. The problem can be solved by restricting the social facts thesis to legal rules, rather than applying it to all legal propositions. Properly construed the social facts thesis does not apply to facts about what legally ought to be the case