This news link posted on Yahoo Dec 27th about reduced Canadian gas exports.
http://ca.news.yahoo.com/s/reuters/business_usa_gas_col
I don't see any reference to NAFTA.
Is there some fexibility in the NAFTA requirements?

As I understand it, exports can be reduced under NAFTA as long as the reduction is a consequence of unimpeded market forces. It is government regulation of exports that is subject to the rules in Article 605.