Here is an interesting article on fighting etiquette.
Buffalo Sabre Alexei Zhitnik was boarded by St. Louis Bluesman Dallas Drake a few days ago (Zhitnik will miss the rest of the regular season). Drake then had to fight Sabre Adam Mair. The theory goes that by Drake fighting Mair, the rest of the Blues stars would not be targeted by Buffalo.
The article really goes into the intricacies of hockey fighting. Maybe someday someone will codify all of the unwritten rules of hockey.