The reform program outlined by regulators and supervisors after the financial crisis implicitly aims to create a new model for banks, one where they are small(er), simple(r) and separable. The drive toward “separability” threatens to diminish the scale and scope economies that global banks...

Capital is controversial. Banks complain that regulators demand too much. Critics complain that banks have too little. A few lone voices contend that banks have just about enough, thanks to the regulatory reform measures taken over the past decade in the wake of the financial crisis. Who's...