UPDATE: 31 October. What I am arguing here is none too clear even to me; so don't spend too much mental energy on it. I make some moves that need further defense even if they do turn out to be defensible. Rather than delete the post, as I am inclined to do, I will leave it for possible reworking later.
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If ignorance of the (positive) law is no excuse, then, I take it, one is obligated or required to know the law, or such portions of it as pertain to one, or perhaps to have on retainer a representative who knows the law or such portions of it as pertain to one. Thus, gun owners ought to know the laws, Federal, State, and local, pertaining to gun ownership, use, sale, transportation, etc. And so the Arizonan who crosses into California with a loaded handgun in his glove box ought to know that what is legal in the Copper State is illegal in the Golden State.
Is the obligation to know the law a moral obligation, a legal obligation, or both? But we ought not assume that there are any moral obligations apart from legal obligations.
Suppose, then, that the only obligations there are are legal obligations: there are no moral obligations as a species of extra-legal obligations. There are no obligations logically antecedent to legal obligations. On this supposition, to be obligated to do X is to be legally obligated to do X in the sense that if there were no positive law that expressed the obligation to do X, then there would be no obligation to do X. Accordingly, the supposition is that obligatoriness collapses into legal obligatoriness.
Now if all obligations are legal obligations, if obligatoriness just is legal obligatoriness, and there is an obligation to know the law, then this obligation is a legal obligation. If so, this obligation must be codified in some law L that mandates that one ought to know the law. L, then, is the positive law that states that one ought to know the law. It follows that L mandates that one know all laws including L. Thus L mandates that one know that L is a law and what it requires. It mandates that one know that it is legally required that knowledge of the laws is legally required.
Now either I know L or I don't. If I don't, then I should since ignorance of the law is no excuse. But how can I be obligated to know a law that I do not know when my obligation to know the law is not something antecedent to the positive law but is expressed only in the actual positive law? This is what is puzzling me.
I am obligated to know L. But this obligation can only be a legal obligation on our supposition. Thus there is a law, namely L, that legally obligates me to know it. But I can be under this obligation only if I know L. If I don't know L I am under no obligation to know it. This is because, on our supposition, the obligation toknow L cannot be logically antecedent to L.
I conclude that our supposition is false, the supposition that the only obligations there are are legal obligations. The obligation to know the law cannot be a legal obligation; it must be a moral obligation. It follows that the moral is logically antecedent to the legal, and does not collapse into the legal.
Now I am quite convinced (for other reasons) that the moral is logically antecedent to the legal. But I am not so sure that above reasoning is correct or even clear enough to be evaluated.
