If an act in inherently morally neutral, but there is a law against it, is it immoral to do it.?

In a question about pot someone made what I believe to be a laughable statement, that breaking the law is morally wrong under any moral code. So, I would like to know what others think. Is it immoral to commit a neutral act that is against the law? What about committing an immoral act becuase the law demands it (for example killing in an unjust war)? What if the government did not have the legal right to p such a law? There is probably no one in the US who wouldn't spend his entire life in prison if every nit-picky little law he or she had ever violated was imposed upon him and the penalties ran concurrently, do any of you feel guilty about this?