Natural Resources Minister Seamus O’Regan says the operation of Enbridge pipeline Line 5  is “non-negotiable,” and the federal government is prepared to “invoke whatever measures we need” to stop Michigan from shutting it down. “We are fighting for Line 5 on every front and we are confident in that fight,” O’Regan said during a testimony before the Special Committee on the Economic Relationship between Canada and the United States on Thursday. “It is an operational pipeline that not only employs people in Ontario and in Alberta and in Quebec, but provides energy security to those provinces and to U.S. states as well.”  The Line 5 pipeline, which crosses Wisconsin and Michigan, brings oil from Western Canada east, where it is refined in Sarnia, Ontario, into products like gasoline, diesel, and home-heating fuel. Shutting down Line 5 would have a major impact on the crude oil supply of Eastern Canada and …