Peeking into the rock

This is because of a story I am reading. In the story a minor boy shot and killed a man who was threatening another minor boy. They are cousins, and they live together: the first boy's parents are the guardians of the second boy. The lawyer for the boy who did the shooting tells him that since his cousin is a witness to the event they will be kept separate and incommunicado until the trial is over in about six months.

I don't believe this for a moment. It has, in fact, ruined the story for me.

Does Canada in fact have such a law that the witness for the defense is to be removed from all contact with the accused until; the trial is over?

I would have thought that they would keep them from talking to each other until they'd made their first statements, at the most.