What topic does section 76 of the Indian Penal Code deal with?

I. Nothing is an offence which is done by a person who is bound by law to do it.

II. Nothing is an offence which is done by a person who by reason of mistake of fact in good faith believes himself to be bound by law to do it.

In the first position protection of S. 76 is very much available, to subordinate officer. However in second situation subordinate officer is not bound by law, but because of mistake of facts, he believes in good faith that he is so bound; therefore protection of S. 76 is available to him. Thus first part of S. 76 deals with legal order while second part with an otherwise illegal order which has been mistaken as legal.