General view of the Imperial Oil refinery, located near Enbridge's Line 5 pipeline, which Michigan Governor Gretchen Whitmer ordered shut down in May 2021, in Sarnia, Ontario, Canada March 20, 2021. Picture taken March 20, 2021. REUTERS/Carlos Osorio/File Photo/File Photo
CALGARY, Alberta, Oct 4 (Reuters) - Canada on Monday formally invoked a 1977 treaty with the United States to request negotiations over Enbridge Inc's