There won't be any specific mention of a percentage in the NAFTA agreement as it is determine by a rule.

If Canada were to impose an export restriction on natural gas (or any other defined petroleum product), it could do so only if maintains an export level greater than or equal to "the proportion prevailing in the most recent 36-month period for which data are available prior to the imposition of the measure, or in such other representative period on which the Parties may agree".

The 56% figure given for natural gas would be based on the recent level of exports.

Further, the percentage is based on "total supply", which the agreement defines to be domestic production plus imports. This would be interesting if LNG terminals are established in Canada for gas that is solely destined for export to the US (as has been the case in several proposals).

I believe that the Parkland Institute is quite aware of specifics of the Proportionality article, but the media are not. No doubt Parkland's message has been somewhat distorted by the media's penchant for dramatic sound bites.

Parkland has been trying to raise the awareness of Canadians, especially in Eastern Canada, about Canada's lack of a domestic energy policy and in particular our loss of energy sovereignty. Most Canadians are complacently unaware of our true energy situation and the risks we are running. Their recent paper calling for the establishment of a Canadian SPR got considerable attention in Quebec, the province that is most dependent on foreign imports.