German bf arrested for harassment in Canada

My German boyfriend has the same problem. He was arrested (and still in jail for 5 days now) for harassment filed by his ex wife who is apparently in Canada. I dont understand why they are still keeping him there. What happened was he went to his ex-wifes house, ex wifes lover opened the door but he slammed it close on him. They had a bad divorce back in the 90s. My bf found his exwife with this guy on their bed that caused the divorce but they didnt have like a real closure about it. What could happen to my boyfriend? He is just there for a project. He is not based in Canada. Do they have grounds on keeping him there for a long time? Im much worried about him and so is he. Please help.