Answer: in fact, (if you are very serious with defintions) there is no moral law, and consequently, it cant’ be broken (say less for an immoral one!), and further, there’s naturally no justification for such a thing. Moral is a behaviour, as it depends, in definition, from a principle that determines a behaviour regarding its innocence or guilt.
A ‘killing’ can be moral in some cases, but it will usually stay illegal except in cases of war or where death penalty is allowed. A ‘moral crime’, can’t be justified by any law, but just by the very innocence in which a human being is acting.
Laws are determined rules of social behaviour which are submitted to punishment in cases of infringement. It may be discussed whether moral innocence may put a human beyond human justice. I wouldn’t say so. But sometimes, precisely because there is innocence, human justice can not gather enough proofs in order to determine the guilt of the responsible.