The RCMP was particularly suspicious of people associated with peace movements—and of political leaders willing to speak openly with people across the political spectrum. In the eyes of Canada’s security establishment, listening to dissenting voices and engaging opponents were not signs of democratic strength. They were grounds for surveillance. The irony is striking. The authorities treated Tommy Douglas as a possible threat largely because he practiced the openness, tolerance, and democratic engagement that Canada claimed to value.

If anything could keep sleep-deprived President Trump busy threatening new tariffs it is likely to be Europe’s decision to remove…