The ruling against Calpine ( CPN) in a dispute with creditors Tuesday could leave the debt-strapped power producer with a hole in its finances. In a closely watched case, Chancery Judge Leo Strine ruled that Calpine violated the terms of a bond indenture when it spent $313 million last summer to buy natural gas to run its power plants. Bondholders argued that the money, raised from an asset sale, was collateral on their loans and couldn't be spent in this fashion to fund day-to-day operations. News of the decision had investors running for the exits, with shares of Calpine falling 31 cents, or 17%, to $1.44 in frenzied trading. The stock was halted after the ruling came out. The judge, in a 44-page ruling, said there were strict limits on how Calpine could use the money, which came from an $850 million asset sale in early July. Strine said buying natural gas was not one of the permitted uses and barred Calpine from making any further purchases. "Calpine's proffered interpretation ... is erroneous," said Strine. "It may not proceed to make further purchases of this kind." The bondholders had contended that the money raised from the asset sale should have been spent on something else, preferable a debt redemption. Calpine currently has about $17 billion of outstanding debt. The judge left open the issue of how Calpine must rectify the situation, noting that not all the aggrieved creditors had joined the litigation. But he said a "restorative remedy is in order." One thing Calpine won't be able to do is resell the natural gas it purchased. As the judge observed: "Calpine has burned up in its power plants all the $313 million worth of the natural gas." A few hours after Strine's ruling, Calpine issued a statement that seemed at odds with the judge's decision. In a press release, the company said it is "still permitted to use its natural gas asset sale proceeds to purchase certain natural gas assets."