This should help:
[Joel Bakan, a law professor at the University of British Columbia, said there is no constitutional basis for cutting off gas between provinces.
"I can say with absolute confidence that Alberta will lose this case," Bakan said.
The Constitution Act of 1867 says that a province cannot interfere with interprovincial trade and commerce, he said.
"Over the years, the courts have carved out ways in which provinces can take care of their own [legitimate] interests ... but there is no authority for provinces to actively discriminate or retaliate against a province by cutting off interprovincial trade.](https://www.cbc.ca/news/canada/british-columbia/alberta-will-lose-this-case-turn-off-the-taps-law-would-be-unconstitutional-says-legal-expert-1.5101561)