BRAMPTON, Ont. - A judge who found a teenage rugby player guilty of manslaughter in the death of an opposing player says the sports field is not a "criminal law-free zone."

Manny Castillo, 15, died from a head injury a few days after he hit his head on the field during a junior rugby game in May 2007.

Ontario Justice Bruce Duncan found the now 18-year-old player guilty of manslaughter today.

In handing down his ruling, Duncan said the laws of Canada apply equally on the playing field as off.

The Crown successfully argued that the accused, then 16, committed manslaughter when he lifted Castillo into the air, his feet facing upwards, and then drove him head first into the ground.

Family members and supporters broke into tears as the verdict was read.

"The defendant intentionally applied force that was outside the rules of the game or any standard by which the game is played," Duncan ruled.

"The defendant committed an assault, an unlawful act. That unlawful act caused death. The defendant is therefore guilty of manslaughter."

The defence had claimed their client acted in self-defence and told the judge Castillo knew he was playing a physical sport and consented to having physical force exerted against him.

"The playing field is not a criminal law-free zone," Duncan said Thursday.

"The laws of the land apply in the same way as they do elsewhere."

Duncan told the court that he accepted the evidence of the game's referee that the accused -- who had played aggressively and fought with referees during the game -- jumped up after injuring the victim and essentially admitted what he had done.

The referee testified that he heard the boy say, "pile drive him hardest I could into ground."

Another witness testified that the accused said, " he was choking me so I picked him up and slammed him into the ground."

The accused had pleaded not guilty in the judge-alone trial.