Generally, it seems that the normativity of law is hypothetical. That is, the norms law imposes are all phrased in terms of conditionals: if you want x, then y. So, for example, if you want to stay out of jail, then don't kill people. If you want to buy a house, then you must be 19 (depending on jurisdiction). And so on and so forth.
However, generally, morality is seen to have a categorical force. That is, the norms morality imposes are all phrased in non-conditional ways: do y. Do not kill. Do help the poor. And so on.
Since the normativity of morality is categorical, and the normativity of law is hypothetical, then it seems that morality will always trump the law. The law will always be exerting a lesser normative force than morality.
This seems far too pat to me (and I came up with it!), but I can't see where the argument's going wrong. Perhaps it isn't? If it isn't, then civil disobedience is always justified, and there is never a moral obligation to obey the law. These are, on the face of it, counter-intuitive results. But, perhaps we should accept them.