What is interference in hockey?

The NHL Rulebook has two pages worth of interference interpretations, which makes it hard to quote from it like the rest of our articles about NHL penalties. Hockey Canada has a more clear understanding of the rule in their book, which is what we will use to break it down.

1. Interferes with or impedes the progress of an opponent, who is not in possession of the puck,
2. Delivers a “late hit” to an opponent,
3. Deliberately knocks a stick out of an opponent’s hand when they are not in possession of the puck, or
4. Prevents an opponent who has lost or dropped their stick or any other piece of equipment from regaining possession of it.

Interference is also the name of the penalty when a player halts the progress of a goalie when he's in his crease. A charging penalty can also be assessed on a hit on the goalie, but most times it's called goaltender interference when it isn't as aggressive.

The Hockey Eastern Ontario Officiating Program did a good job of explaining the interference penalty. The duration of the video shows how in-depth the penalty is, as there are many different interpretations. Interference is one of the most argued and talked about penalties when they are called, as it's under the referee's discretion whether a hit was late or serious enough to warrant a penalty.

Goalie interference is also a penalty that gets argued the most. The addition of video review to the NHL has made the penalty and/or ruling even more controversial, as referees watch the tablet and still get the call wrong in the eyes of some people.

The reason I say penalty and/or ruling is that goalie interference calls don't always end in a penalty. Sometimes the player interferes with the goalie's ability to stop the puck but it isn't blatant enough to get a two-minute minor penalty.