The rules penalize fighting--so technically it's illegal--but not so stringently that it is discouraged completely. A major penalty (5 minutes) is the harshest penalty a referee can dish out without ejecting someone from the game (game misconduct), but since both combatants will receive the same penalty, there is little on-ice repercussion to a team when a player fights. read more
Fighting has been a part of ice hockey since the sport's rise in popularity in 19th century Canada. There are a number of theories behind the integration of fighting into the game; the most common is that the relative lack of rules in the early history of hockey encouraged physical intimidation and control. read more