I'm inclined to think, yes, that if a law is unjust it should lose its status as a law, but it doesn't immediately follow that one has no obligation to follow that law. In the case of profoundly unjust laws, such as those regarding Jews in Nazi Germany, presumably it would, at least, be permissible not to follow the law. But there are many other laws that might be regarded as unjust that are far less oppressive. One might suppose one had an obligation to follow such laws out of a kind of respect for the law. What one ought to do instead might be to attempt to get the law changed. Of course, in some cases, publicly and openly refusing to follow the law might be a way of drawing attention to its injustice: That's civil disobedience, in its simplest form.