It is fitting that the European Commission is finally set to propose a carbon border tax on France's national holiday on July 14: Bastille Day. It was, after all, the French who led the charge for a revolutionary new levy to be imposed at the EU's ports and border crossings to shield Europe's industries from cheaper imports made in places with laxer environmental rules. As with the original Bastille Day at the beginning of the French revolution, however, the big question is now whether everything will descend into a bloody spate of feuding where many of the nobler intentions behind the reform are lost. The biggest danger is that the proposal will be diluted beyond recognition amid a series of compromises to please opponents ranging from trade partners like the U.S. and China, through to Europe's own domestic industries.