Forget the Volcker Rule.

No, not because it’s a politically inspired idea, dusted off and presented to Main Street as the solution to the problems on Wall Street after an angry bunch of voters elected a Republican to fill what should have been a safely Democratic Senate seat, the one left vacant by the death of the late Senator Edward Kennedy. Not because the proposal to force banks to walk away from proprietary trading and too-close dealings with private equity and hedge funds doesn’t have the force of law and no one has yet tried to frame legislation that would reflect these ideas. Not even because it might be a good idea or because the odds are heavily stacked against former Federal Reserve Chairman Paul Volcker’s brainchild winning enough support in Congress to become the law of the land.

The biggest problem with the Volcker Rule is that it attacks the wrong part of the regulatory conundrum that is Wall Street. Yes, being "too big to fail" generates risks for both the financial system and the politicians who will be called on to bail out any giant or systemically crucial financial player that can’t manage risk. Yes, it may be a desirable for at least some of these giant and systemically important institutions to walk away from business lines that aren’t central to their core commercial-banking operations, if persisting in those businesses increases the risk that the government will be called on to make good on its no-longer implicit guarantee of their solvency. And perhaps it would have been better had the Glass-Steagall Act of 1933 never been modified or repealed, keeping commercial banks out of investment-banking territory and vice versa.

But the Volcker Rule deals with Wall Street’s structure: who owns what kind of businesses, which firms can conduct certain activities, and what kinds of rules will govern their behavior. Structural reforms are helpful and probably necessary, but they don’t go to the heart of the problems on Wall Street. Changing the rules of the game without trying to change the way its participants think about the reason they are playing and their definition of "winning" leaves untouched the real problem: the fact that Wall Street operates with the sole objective of making as much money as possible, as rapidly as possible, for their investors. That’s their fiduciary duty; the same one that confronts every other publicly traded corporation.

The problem with that shows up in one of the most-criticized parts of the behavior of Goldman Sachs at the peak of the subprime crisis. The firm’s in-house risk managers had already become concerned about what was happening in the market, about the weird structures and poor credit quality of the loans that made up an ever-growing part of the mortgage-backed securities being repackaged and sold as blue-chip collateralized debt obligations (CDOs).

Of course, Goldman didn’t stop selling those CDOs. That would have meant walking away from a lucrative business and been incompatible with their fiduciary duty to investors to maximize the investment bank’s profits. But, while it continued to sell securities it didn’t want to own itself to its clients, it sold the same subprime investment short on a proprietary basis—a bit like bartender peddling rotgut to customers while keeping a stash of premium Bourbon beneath the counter to drink himself.

Goldman’s reluctance to consume its own cooking may have saved its skin, but it has put the investment bank in the hot seat with the public and with Phil Angelides, chairman of the Financial Crisis Inquiry Commission. Why, Angelides, demanded of Goldman Sachs CEO Lloyd Blankfein during the first round of FCIC hearings last month, hadn’t Goldman Sachs looked out for its clients? Why hadn’t it refrained from doing something that “doesn’t sound like a good practice for the market”?