This is where Harper's incompetence will come back to bite.  As a part of the 2006 Softwood  "deal" which Harper rushed through (just so he could brag about "getting things done"), Harper gave up all previous court wins for Canada.  Simply threw them out so they can never be used in any future dispute.

Canada had an overwhelming number of court wins achieved over decades by various Govt's (Liberal and Conservative).   NAFTA tribunal decisions, ITC decisions, even the US Dept of Commerce ruled in Canada's favour that the US countervailing duties were unlawful.     All of those hard fought legal wins were tossed in the trash just for expediency (Harper allowed the US to keep $1 Bln of the collected duties on top of all this).  Few people noticed this at the time because the Harper Govt was too busy celebrating (multiple times) and propagandizing the "deal" (which saw its first dispute 1 yr later.)

Canada is correct to get ahead of this, since we've already given up a lot of ammunition.