The US Federal Reserve Bank wants Congress to limitWall Street's ability to own physical commodities, among other things, because of the risk to the global financial system. 

In a report released Thursday, the Fed also pushed for a ban on merchant banks buying stakes in companies rather than lending them money.  These ideas came from a multi-agency investigation into loopholes and cracks in the Dodd-Frank Act, which was designed to correct the willy-nilly deregulation of the financial sector that led to the 2008 global financial crisis.

Wall Street firms have been scaling back riskier parts of their commodities businesses in recent years due to public and political scrutiny over the role of banks in raw materials markets.  But the existing allowing commodity investments are still raising "safety and soundness concerns as well as competitive issues," according to the Fed.