(Dow Jones) It may seem like a big win for U.S. taxpayers, but a new Swiss court ruling in the UBS AG tax evasion case is not likely to help those who hid money from the Internal Revenue Service in Swiss bank accounts.

That includes those who already have turned themselves in to tax authorities, or those still harboring secret accounts at various Swiss banks.

Nonetheless, the ruling is causing an uproar among some Swiss account holders, who think they may gain from it.

A court panel in Bern said Friday that UBS files on private-bank clients shouldn't be turned over to U.S. authorities. It has called into question a settlement that allowed U.S. prosecutors to crack Swiss bank secrecy; and, it could reverse part of a settlement struck last year that called for UBS to eventually disclose the identities of 4,450 accounts tied to Americans.

Specifically, the court ruled that under Swiss law, failure to file a W-9 form isn't considered fraud in Switzerland, as it would be in the U.S.

That is at odds with a provision under an earlier settlement between the U.S. and Switzerland. In it, Swiss officials agreed that if a U.S. taxpayer had violated Swiss law, his confidential records could be turned over to the IRS and Justice Department. An important indicator of fraud, according to the agreement, was a failure by U.S. taxpayers to file a W-9 form. (The W-9 tells a bank or broker that a customer is a U.S. taxpayer. Foreign firms must obtain them from customers who are U.S. taxpayers if they want to do business with the U.S.)

Scott Michel, an attorney at Caplin & Drysdale in Washington, D.C., who is representing UBS account holders, said he doesn't see the ruling changing the picture for those still harboring a secret account who are on the fence over whether to turn themselves in. First, it remains to be seen whether the decision will ultimately prevent the turnover of the UBS information at issue, he said. The Swiss Federal Council is expected to issue a decision on Wednesday, and then the U.S. will react.

More to the point, said Scott, people with undeclared foreign accounts still each year must confront the prospect of filing a tax return. They risk engaging in criminal activity by failing to report investment income on the account, particularly "now that the IRS has been so aggressive, and public, in pursuing issues regarding undeclared accounts," he said.

As for U.S. taxpayers with UBS accounts, the IRS and UBS are already talking about how the bank will continue to hand over names under the settlement agreement, reached in August after a long U.S. investigation into how UBS allegedly helped U.S. clients dodge U.S. income taxes. The inquiry led to an agreement that called for the identification of the UBS clients.

The investigation also prompted thousands of U.S. taxpayers to turn themselves in to the IRS in hopes of gaining some leniency on penalties.

UBS and the IRS "are not bound by the terms of the prior Swiss-US treaty and they will find a way to keep the information flowing," said Bryan Skarlatos, a partner at law firm Kostelanetz & Fink, who is representing UBS clients.

For U.S. taxpayers at other banks, the new Swiss-IRS treaty has a more expansive exchange of information provision, and "the IRS has ways to squeeze the information out of the Swiss banks outside of the treaty process," said Skarlatos.

"The treaty provisions are not the only way to skin the cat," he added.

Skarlatos said he has had to tell clients excited at the possible ramifications of the ruling that it won't make much of a difference.

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