Specifically, NHL Rule 46.6 provides as follows:
Helmets — No player may remove his helmet prior to engaging in a fight. If he should do so, he shall be assessed a two minute minor penalty for unsportsmanlike conduct. Helmets that come off in the course of and resulting from the altercation will not result in a penalty to either player.
The flaws in the rule were revealed recently when Brett Gallant of the New York Islanders and Krys Barch of the New Jersey Devils removed each other’s helmets before a fight.
Here’s the surreal video: