See the two November 21 memorandums.
http://www.whitehouse.gov/briefing-room/presidential-actions/presidential-memoranda
In turn Secretaries put out directives.
The 2, Nov 21, memos do not authorize amnesty. He gave a verbal order to Jeh Johnson who in turn submitted a directive to the federal registry to authorize amnesty. He knows what he is doing is illegal. He does not want his signature on any documentation that could later be used against him.
Thanx