Though we can in principle disobey unjust laws, we should recognize the inherent difficulty in determining whether a law is unjust. It is one thing for law to be unjust and another for you to know that it is unjust. Civil magistrates are necessary, as I’ve said, because of natural epistemic limitations in individuals to determine expedient actions for the common good. How then can a private person reliably determine whether a law is unjust?
