An ethos is a test to determine whether some controllable, deterministic eventual outcome is good (ethical) or bad (unethical). Ethical study is the process by which an ethos is derived.
Morality is the mapping of a sentient, autonomous individual's actions onto an ethos in order to determine the sets of actions that are right and wrong. If an action is moral, it is necessarily ethical. An action can be moral or immoral depending on circumstance, because the same action can have different outcome events in different contexts. If the individual, as a sentient being, had knowledge or could have reasonably predicted that the outcome of his action would have been an unethical event, the act was immoral. However, given an action with mixed ethical outcomes, is an action both moral and immoral, or does the greater moral direction dominate the act into a binary classification?
Legality is often misconstrued as the forceful encoding of a morality. In fact, what is legal is not necessarily moral, simply because government force cannot be efficiently and accountably used to stop certain acts. And what is illegal is not necessarily immoral, because government is not always accountable and democratic. There must be a significant overlap for the government not to be overthrown, but morality and legality are not a 1:1 mapping in any real world society.
The argument that something is immoral because it is illegal is thus a weak argument. The assumption must be made that following the law is ethically right. Since the law is made by men, that ethos is a framework for manipulation and control by those who act immorally relative to the subject.