With regard to the Kielburgers, who refuse to appear even though they have been summoned by the committees, I'll read the passage from the House of Commons Procedure and Practice that you referred to today:
... the House of Commons possesses the right to confine individuals as a punishment for contempt, although it has not exercised this authority since 1913. In the years immediately following Confederation, the House ordered the Sergeant-at-Arms to take individuals into custody on four occasions and ordered the imprisonment of others. Again in 1913, the Sergeant-at-Arms was ordered to imprison an individual.
I agree that we don't want to imprison anyone. However, I just want to confirm in French what you already said in English. At worst, if a witness refuses to appear after receiving an order from Parliament, we have the power to turn to the Sergeant-at-Arms and even the police to compel the witness to appear.