The legal crusade against the Liberals’ greenhouse gas pricing “backstop” came to a dead end early Thursday. The Supreme Court of Canada has ruled 6-3 that Ottawa can, without violating the Constitution, require provinces to impose carbon taxes at a particular level and collect federal levies in ones that don’t. This required lawyers for the federal government to convince the court that they have a right to invoke what the pros call “POGG”: the residual “peace, order, and good government” power assigned to the Dominion in the old British North America Act. The result is a slightly funny spectacle. POGG has been explicitly invoked only a handful of times in Canadian history. From fairly early days, the danger that POGG presents to provincial sovereignty has been evident to judges. One accepted avenue for the use of POGG is in matters of inherent “national concern,” a phrase we are stuck with mostly because it appeared in some early, lousy precedents.