WITH RUSSIA’S invasion of Ukraine in full swing, the West is scrambling to respond. That Vladimir Putin, Russia’s president, can back his imperial ambitions with nuclear arms has taken a shooting war with nato off the table. Economic retaliation is the weapon of choice. One obvious move would be to cut Russian banks’ access to swift, a messaging network used by 11,000 banks in 200 countries to make cross-border payments. Some Western governments favor pressing the co-operatively owned swift into cutting Russia off, but others do not. For now, the measure remains off the list of sanctions outlined by the West. Why the reluctance?