The argument was recently put to Diana at Noodle Food in this fashion:
Laws are instituted by some objective process, and by living in this city with other men you've agreed to abide by them. Of course, some laws are unjust (e.g. speed limits apply to public roads, thus being based on another unjust law) but since laws are objectively decided, an individual man cannot morally, or legally, spurn those he disagrees with. Clear enough, right?She replied (in part) as follows:
The Objectivist view is not that "laws are instituted by some objective process, and by living in this city with other men you've agreed to abide by them." Laws in this country are instituted by pull-peddling majority rule, with scant respect for individual rights, even those explicitly enshrined in the [US] Constitution. The resulting laws are often grossly non-objective -- in the sense that you cannot know in advance whether you are breaking them or not...Read on here for her full argument.
Moreover, a person does not consent to the laws of a given government simply by choosing to live within its territory -- particularly not when significantly better alternatives are nowhere to be found. He never agreed to abide by the laws; he may have even resolved to do the opposite in some cases.
Moreover, the Objectivist ethics would never endorse the command "obey the law" as a binding normative principle, as the question suggests. Barring metaphysical emergencies, we are obliged to respect the rights of others. That respect for the independent judgment of others is a matter of self-interest: it is a means of advancing our lives...
In a fully free society, respecting the rights of others means obeying the law, precisely because those laws are just protections of rights. However, when laws violate rights, they can imperil the fundamental values of life, e.g. health, wealth, happiness. In that case, a person cannot be morally obliged to obey them. Of course, it may be prudent for him to obey them nonetheless, given the likelihood of detection and punishment. Yet it would be incoherent say that a person must sacrifice his highest value, i.e. his own life, for the sake of the ill-conceived and unjust products of majority rule.
However, that doesn't morally justify disobeying every unjust law...