Today’s central banks wield extraordinary powers, both monetary and regulatory, and with a capacity to substitute for elected governments tempted to pass the buck. Debates about central banking’s powers and legitimacy barely touch, however, on whether and how monetary independence fits with the values that drive constitutionalism. It turns out that, for modern economies using fiat money, independence is a corollary of the higher level separation of (fiscal) powers between the legislative and executive branches. Even though independence is necessary, it needs to be carefully constrained by a “money-credit constitution.” Those general arguments, applicable in liberal democracies, do not carry across cleanly to the euro area. A principled case can be made for the ECB’s mandate being specially tight, but that is in tension with its de facto role as the emergency economic actor for the euro area. Facing up to that will be necessary sooner or later.