FROM lamp-posts all over Dublin, a nice-looking woman smiled at passers-by. “It’s simple,” the poster read; “I’m safer in Europe”. What her safety had to do with the Lisbon treaty—a series of technical if important changes to the EU’s internal rule book—was less clear than the veiled threat: Ireland’s European partners were not in a mood to tolerate a second display of dissent, only 15 months after the first.

Pro-Lisbon campaigners hinted that Ireland would be ejected from the European mainstream if it voted No again. Business leaders suggested that foreign multinationals would shun the place (no matter that grumpy, Eurosceptic Britain is an EU champion at attracting foreign direct investment). Such threats had an...