In Parliament, Sevigny became a supporter of Canadian participation in World War I despite the strong opposition of most Quebecers, and became a staunch Conservative.

Prime Minister Robert Borden was facing an increasing divisive crisis over conscription with the country divided between English Canadians who supported the measure and French-Canadians who fervently opposed it.

Sévigny was appointed Minister of Inland Revenue, and was required by the laws of the time to resign his seat and run in a by-election.

The country divided largely along linguistic lines: the Conservative candidates were wiped out in Quebec in a rout that cost Sévigny his seat.

In 1950, Sévigny presided over the murder trial of Albert Guay, who was responsible for the bombing of Canadian Pacific Air Lines Flight 108.