It is speculative. Article does not say how Canadian Solar could be sanctioned. In fact is says very little about CSIQ--almost no numbers which it gives for all the others. It says: (in the body, the "comment" above was part of a summary graphic) "With some plants in Canada, Candian Solar might be able to shift more production there to benefit from NAFTA, though the administration could still choose to punish the company." Article then goes on to discuss SunPower.
Everything that I have read about ITC sort of implies that after the ITC recommends a remidy, the president can do whatever he wants. Usually interpreted to mean he can accept ITC recommendations, or impose lighter or heavier remedies. Not sure if he can single out a specific company, but I'm also not sure he can't--usually it is just assumed no one would try... (Obviously CSIQ could then seek to undo through NAFTA courts or WTO or whoever adjudicates NAFTA stuff based on details of the treaty, but damage would already be done--from the current investor perspective.)