When it comes to Canadian defence policy, there is something poison about the words “missile defence.” The United States attempted to get Ottawa to sign on to its missile-defence program as far back as 2005 when then-prime minister Paul Martin turned the U.S. away after several months of a rancorous debate in Canada. The government of Stephen Harper, which followed, never publicly attempted to join the U.S. missile-defence program. The current government of Justin Trudeau decided not to join the program when the U.S. again attempted to enlist Canada in 2017. Now the question of whether Canada will join the U.S.—and other NATO partners—in mounting a missile-defence program is becoming more pressing as Irving Shipbuilding Inc. in Halifax prepares for the construction of 15 new Canadian S...