IF IT’S a Wednesday, it must be Vestager day. Or so it has seemed this month in Brussels, as Margrethe Vestager, the European competition commissioner, has made ambitious moves against formidable adversaries for three weeks in a row. On April 15th it was Google, which Ms Vestager thinks unfairly privileges its shopping service over rivals. A week later she trained her sights on Gazprom, Russia’s mostly state-owned gas giant, accusing it of unfair pricing and market meddling. And on April 29th Ms Vestager announced a probe into the subsidies European governments provide to electric utilities, some of which she thinks may amount to illegal state aid. Amid constant reminders of the EU’s weakness, from Mediterranean migration to the endless Greek saga, Ms Vestager’s shows of strength are a reminder that Brussels has bite. Ms Vestager, who previously served as Denmark’s economy minister, is clearly a tough cookie. But her impact has as much to do with European law as with her personality. Unburdened by the constraints that shackle most of her 27 fellow commissioners, she can block mergers, launch surprise raids on private offices and threaten...