That would be this rule:
RULE 165 – THROWING A STICK OR OBJECT
ii.
A player can slide or direct any stick or any part of it, or any object,
away from his immediate area on ice so long as his actions do not
interfere with an opponent. However, a player on the ice who throws
or directs a stick or any part of it, or any other object, at the puck or
puck carrier in the neutral or attacking zone, will be assessed a minor
penalty