If nothing else, the collapse of MF Global has made one thing clear: The notion that customer assets were safe was a sham.


MF Global’s customers, who discovered that the firm had plundered $1.6 billion of their property, learned that the hard way. But they aren’t the only potential victims. The loophole that allowed MF Global to convert more than $1 billion in customer property to its own reckless bet on European debt is still in effect — although the Commodity Futures Trading Commission, which regulates futures and commodities brokers, said it had since pressured other firms to stop using it.


The CME Group, which is both the largest commodities and futures exchange and also regulates many brokers, told me this week that when MF Global collapsed last year, four of the 40 firms it oversees were still using an “alternative” calculation of customer assets that vastly understates what firms actually owe. A spokeswoman declined to name them, saying such information was confidential. In my view, they should all be identified publicly so their customers can demand reassurances that the practice has stopped — and that their assets are safe.


Since the Depression, when thousands of customers were wiped out by failing brokerage firms, the idea that customer assets are protected has been sacrosanct, embodied in laws and regulations that require the assets to be safely segregated. Violating these requirements is a crime.


The rules require a firm to put aside the amount it would owe if its customers’ accounts were liquidated. This would seem simple common sense: if a brokerage firm closed or failed, customers should expect to get the full value of their assets.


But the rules apply only to accounts in the United States. In 1987, the commodity commission approved a series of rules governing foreign futures and options transactions, one of which provided an alternative calculation of how much firms needed to put aside for accounts that traded on foreign exchanges.


The alternative calculation almost always resulted in a lower amount — sometimes much lower — that needed to be segregated in foreign accounts, because it covered only options and futures. Cash and securities held in customer accounts didn’t count. So if a customer held only cash and securities, the firm had no segregation requirement at all.


This may not have seemed such a big deal at the time, although even then, futures and options trading by American customers on foreign exchanges was growing rapidly. How and why this provision got into the federal register remains something of a mystery, and in the wake of MF Global’s collapse, no one seems to want to take credit (or blame) for it.


The commodity commission’s chairman at the time, Kalo Hineman, a cattle rancher and former Republican state lawmaker in Kansas who was appointed by President Ronald Reagan, died in 2003. Some regulators said that a tougher segregation requirement for foreign accounts would have been too costly and complicated to maintain given the technology at the time. Others point out that it was better than nothing, which was the prevailing standard for foreign accounts before the rule. A spokesman for the National Futures Association offered that “U.S. participation in foreign markets was small and generally limited to commercial users.”


None of this withstands much scrutiny if the commodity commission really wanted to protect customers. The answer may well be, as one regulator told me, “it’s what the industry wanted,” and that’s pretty much what it got.


Why the futures and options brokers lobbied for such a loophole is obvious: it allowed firms to do whatever they wanted with customer money, including using it to speculate for their own accounts. And by last year, that was no small sum. In his recent report, James Giddens, the MF Global liquidation trustee, showed the difference between the amount the firm had to segregate using the net liquidating method and the more lenient alternative method. On many days, it was more than $1 billion, reaching a peak of $1.25 billion last Oct. 13.