It's the unfortunately tragic side of an often violent sports world: players sustaining fatal injuries in the heat of battle. But a Canadian legal ruling could make players culpable as criminals for on-field fatalities.

The change comes from Ontario Judge Bruce Duncan. He ruled recently in the 2007 death of a high school rugby player, 15-year-old Manny Castillo, who died of head injuries after an collision with another player.

Duncan stated "the playing field is not a criminal law-free zone. The laws of the land apply in the same way as they do elsewhere." Castillo's tackler was convicted of manslaughter.

Though the incident occurred in high school sports, the ruling could set a precedent in the world of professional atheltics where columnists have long expressed fears player deaths--particularly in the National Football League with its history of violent moments and serious injuries.

Recent incidents are only exacerbating these fears. Earlier this year, hockey player Don Sanderson died after hitting his head on the ice during a mid-game fight and lapsed into a coma. Just last year in New Jersey, Montclair High School football player Ryne Dougherty died from complications following an injury. Around the same time in Greenville, North Carolina, high school football player Jaquan Waller collapsed and died as a result of "second impact syndrome," a condition in which two relatively minor head injuries occur successively. Waller's was the third high school football death in North Carolina in seven weeks.

It is unclear how Duncan's ruling will fit in as a legal precedent. Except in the Castillo case, no other athlete has been held criminally responsible in the death of another athlete. But the violence of professional sports almost assures the ruling will be referred to again.