The Supreme Court of Canada never, ever ruled on the matter of Khadr's terrorist activities.  Here's a chronology:  
Aug. 10, 2005: Federal Court judge says Canadian agencies, including CSIS, violated Khadr’s rights by giving information from interviews with him to U.S. investigators.
May 23, 2008: The Supreme Court of Canada concludes Canadian officials illegally shared information about Khadr with the U.S.
Aug. 14, 2009: The Federal Court of Appeal upholds a ruling requiring Ottawa to press for Khadr’s return from Guantanamo Bay.
Jan. 29, 2010: The Supreme Court overturns court orders that the Canadian government should repatriate Khadr, despite agreeing his human rights were violated.
Oct. 25, 2010: Khadr changes his plea to guilty on all five counts.

The above are the only rulings on Khadar from the Supreme Court of Canada - none address whether or not he is guilty of terrorism.  The only court ever to hear his terrorism charges ruled him guilty and sentenced him to 40 years.