"Harnessing the tension between "equity" and "efficiency" and achieving the optimal equilibrium between these policy objectives, has long been one of the major questions bedevilling economics and, more generally, political philosophy in liberal democracies but also beyond."

In recent months, the European Commission has faced a surge in protectionist moves by Member States designed to protect national companies from foreign acquirers. To resist those attempts, it has relied on a relatively peculiar yet theoretically powerful tool: Article 21 of the EC Merger...