Tensions between a president and a Federal Reserve chairman are nothing new. Up until now, they may have reached a peak when Lyndon Johnson shoved William McChesney Martin at the LBJ ranch. Martin gave in a while later, another step into the inflationary quagmire from which the U.S. emerged only after Paul Volcker reasserted the Fed’s independence. However bad that Texas moment, it falls far short of the Department of Justice’s serving the Federal Reserve with grand jury subpoenas on Friday. They relate to testimony given to the Senate Banking Committee concerning an over-budget renovation project and come with the...