Very sticky ground and one where an individual has to weigh up which is more serious, possible breach of national law (for refusing an order) or possible breach of international law (for carrying out an order).
I agree Helpful Stacker (we had a similar discussion about the rights and wrongs of 'following orders' in a previous thread relating to the shooting down of a Syrian helicopter).
Out of interest, is it not national law to disobey an unlawful order?