Congress is busy hammering out a financial reform bill, and JPMorgan Chase (NYSE: JPM) just reminded everyone how important it is.

Part of this bill is the Volcker Rule, named after former Fed boss Paul Volcker, which bans taxpayer-backed commercial banks from proprietary trading, or trading for their own account (as opposed to facilitating client trades).

If you're wondering why there's a movement to ban such activity, check out rumblings that JPMorgan just lost as much as $250 million on a single proprietary trade. Even in JPMorgan's world, this is real money. And what kind of trade was this? Adding liquidity to the mortgage market? Digging for price discovery in the small business loan market? No sir. As the New York Post writes:

Specifically, the firm's traders were believed to have been wagering on the differentials between the costs associated with shipping coal in northwest Europe and the price of delivering coal in South Africa's Richards Bay.

This is pure gambling, plain and simple. Try arguing that it isn't. Go ahead. Try.

Now, no one's saying we want a prohibition on risk-taking. But all the big trading banks -- JPMorgan, Citigroup (NYSE: C), Bank of America (NYSE: BAC), Goldman Sachs (NYSE: GS), and Morgan Stanley (NYSE: MS) -- are able to pull off these trades with taxpayer-backed capital in one way or another. 

You can still gamble your own money. But once you've lassoed and hogtied the support of the common citizen, your freedom to do stupid things is revoked. That's all the Volcker Rule says.

In most states, playing blackjack with your own money is illegal. On Wall Street, using subsidized money to throw the dice on shipping spreads is free game. Let's pass the Volcker Rule.

Fool contributor Morgan Housel doesn't own shares in any of the companies mentioned in this article. The Fool has a disclosure policy.