According to the NHL rulebook:

Rule 52 – Slew-footing 52.1 Slew-footing - Slew-footing is the act of a player using his leg or foot to knock or kick an opponent’s feet from under him, or pushes an opponent’s upper body backward with an arm or elbow, and at the same time with a forward motion of his leg, knocks or kicks the opponent’s feet from under him, causing him to fall violently to the ice. 52.2 Match Penalty - Any player who is guilty of slew-footing shall be assessed a match penalty.

However, I might be missing something or it could be that the rules vary between leagues.