Interference is when a player commits any of the following actions:
- Interferes with or impedes the progress of an opponent, who is not in possession of the puck,
- Delivers a “late hit” to an opponent,
- Deliberately knocks a stick out of an opponent’s hand when they are not in possession of the puck, or
- Prevents an opponent who has lost or dropped their stick or any other piece of equipment from regaining possession of it.
Sorry, I like checking wording of rules sometimes. That example fit into point 1, but that sorta play happens a lot.
I did however learn that trying to pile snow in front of the crease is a minor penalty classed as Interference. Didn't Fleury try doing that and he got a chuckle and a "don't do that" from the ref?