  The fulcrum and central question of natural law theories of law is: How and why can law, and its positing in legislation, judicial decisions, and customs, give its subjects sound reason for acting in accordance with it? How can a rule’s, a judgment’s, or an institution’s legal (“formal,” “systemic”) validity, or its facticity or efficacy as a social phenomenon (e.g., of official practice), make it authoritative in its subject’s deliberations? 