Senators Warren and McCain have introduced legislation to prevent banks from engaging in certain financial speculation. Its explained in this article by Peter Eavis. Here's a brief excerpt:
Senator Elizabeth Warren on Thursday introduced an aggressive piece of legislation that intends to take the financial industry back to an era when there was a strict divide between traditional banking and speculative activities. The bill, which is also sponsored by Senator John McCain, Republican of Arizona, and two other senators, is named the 21st Century Glass-Steagall Act. Its intention is to create a modern version of the seminal Glass-Steagall legislation from the 1930s, which placed firm limits on what regulated banks could do. It was fully repealed in 1999, laying the groundwork for the mergers that created some of the biggest banks of today. If passed, it could force many of those banks to let go of their trading operations.