Today the Senate Banking Committee met to discuss Wall Street's role in the global commodities business, and as you can imagine Senator Elizabeth Warren (D-MA) was quite outspoken about the fact that she wants it majorly diminished.

"...I share the concern of many of my colleagues about asset managers at huge Wall Street banks exercising control of key parts of America's infrastructure," she said.

This discussion is crucial, as all of that will come up for consideration in September.

Back in 2003 the Federal Reserve decided to temporarily allow banks to purchase commodities directly. That means oil, power, copper, aluminium etc. This September, that temporary regulatory relaxation is set to expire, and if it does, a big chunk of Wall Street's business will expire with it.

And now that the ruling is up for discussion, Congress gets to weigh in. Wall Street be warned, if this hearing was any indication, the Senate is coming down on the side of culling the commodities business.

Warren decried the idea that banks would use "other people's money" in pension and retirement savings "to pave the way for big banks to be able to control an electric plant or an oil refinery."

One witness at the hearing asked her simply — what would have happened if a bank had owned the Exxon-Valdez?

If that general tone sounds ominous, recent news stories haven't helped. This weekend, the New York Times reported that Goldman Sachs has allegedly been using its aluminum warehouses to manipulate the price of the metal.

Additionally, JP Morgan is in negotiations with FERC, a federal energy regulator, to settle charges that its traders manipulated energy markets in the western U.S., they could pay up to $410 million.

For today's hearing, Senators heard testimony from Ms. Saule Omarova, Associate Professor of Law University of North Carolina at Chapel Hill School of Law; Mr. Joshua Rosner, Managing Director Graham Fisher & Company; Mr. Timothy Weiner, Global Risk Manager Commodities/Metals, MillerCoors LLC; and Mr. Randall D. Guynn, Head of Financial Institutions Group.

Aside from Guynn, all of the witnesses cautioned against renewing the Fed's 2003 decision. Omarava was especially damning, saying that when Congress separated banking from commerce in 1956, they sought to prevent markets like the one we're in.

"In this... over the counter derivative oil market I suspect Goldman Sachs can actually manipulate price," said Omarava. "They could also affect the price of physical oil if they own tankers... I'm all for the DOJ launching an anti-trust investigation into these matters... If this is the market where JP Morgan and Goldman Sachs are playing, it makes me very uncomfortable as a banking attorney."

Omarava also expressed doubts that regulators would be able to catch this activity as it's so complex.

The witnesses didn't just talk about prices either, they talked monopolies. Since her rise to prominence as a regulator and then a Senator, Warren has been saying that banks are getting too big, too interconnected, and too complicated. Rosner's testimony corroborated that idea, and added to it the specter of commodities -controlling, all-encompassing banking behemoths backstopped by the government (too big too fail).

It's just more "coddling" from the Fed, he said, later adding... "These institutions have become the equivalent of the government institutions we saw fail during the crisis."

This isn't to say that Warren's going to give up her crusade to bring back Glass-Steagall and pick this up as her mantle — she's not. At the hearing she said that it was just "one tool in a tool box" to bring Wall Street back down to size.

There's a difference between the reinstatement of Glass-Steagall and this commodities issue though, and that difference is all that matters to Wall Street banks.

Where trying to reinstate Glass-Steagall seemed like a matter of lobbying and politicing, taking Wall Street out of the commodities business is seen as a matter of dollars. It impacts the Street's bottom line — if it didn't, Goldman wouldn't have put out a "fact sheet" on its involvement in the aluminum warehouse business.

This actually makes bankers nervous.

Watch video of Warren's portion of the hearing below: