Open this photo in gallery: TikTok on May 22 filed suit in a U.S. federal court to stop the state of Montana from implementing an overall ban on the video sharing app.PATRICK T. FALLON/AFP/Getty Images Gus Carlson is a U.S.-based columnist for The Globe and Mail. Call it Big Sky v. Big Spy. As Montana regulators and TikTok lawyers prepare to square off in court over the state’s banning of the social-media platform on grounds it is a spying mechanism for the Chinese government, there is more at stake than U.S. national security. The case will test how far government...