France’s violent Yellow Vest protests are now about many domestic concerns, but it’s no accident that the trigger was a fuel-tax hike. Nothing reveals the disconnect between ordinary voters and an aloof political class more than carbon taxation.

The fault line runs between anti-carbon policies and economic growth, and France is a test for the political future of emissions restrictions. France already is a relatively low-carbon economy, with per-capita emissions half Germany’s as of 2014. French governments have nonetheless...