It seems shocking to me that these things happen to anyone, anywhere at any time..whether or not they are innocent or guilty.
Innocent until proven guilty should be the method used in any action and if evidence is available then they should be "tried" for want of a better word, immediately or as soon as possible so that they may not be held, if innocent, for any length of time.
Is Maher Arar innocent? Has it been proven either that he has or has not been involved with al-qaeda? I assume, as you say he is an innocent man that proof of that must be available or that absolutely no proof exists that he is.
If that is true then it is a total travesty of justice and really does need looking into...the same thing could happen to anyone.
Best wishes.