Jeff Gray, a union leader for Canadians working for GM, has a message for companies considering moving auto jobs to the United States in response to President Donald Trump's tariffs. Gray said his great-grandfather was a founding member of the union in 1937,

Mr. Trump on Wednesday unveiled a main plank in his protectionist policies, declaring imported cars a threat to national security and slapping them with tariffs as high as 25 per cent starting April 3. Auto parts will also be taxed as of May 3 or later.

General Motors shares fell more than 7% Thursday as investors weighed the auto giant’s outsize vulnerability to the tariffs President Donald Trump announced Wednesday.