The biggest mistake was Chretien pressing the Pakistani government so hard to release his known terrorist father Ahmed Khadr from prison at the onset. 

Liberals conveniently want t forget this important fact. 

Chretien didn't do the smart thing leaving him where he belonged but instead vouched for Ahmed to return to Canada enabling him to continue radicalizing the entire Khadr family.

If it wasn't for Chretien's blunder and intervention we wouldn't be dealing with all this mess in the first place let alone dealing with the Liberal's compliance with the US early on to house Omar in Gitmo to hopefully sweep Chretien's initial mistake under the rug.