Beleaguered Federal Reserve Chairman Jerome Powell got succor recently from an unlikely source, the Bank for International Settlements in Basel, Switzerland. It seems that the BIS consortium, which fosters cooperation and regulatory coordination among the world’s central banks, is getting worried about the political demands on its constituents.

A Wall Street Journal article last month quoted the BIS annual report as asserting that “monetary policy can no longer be the main engine of economic growth, and other policy drivers...