Last week, UBS announced that a rogue trader caused it to lose more than $2 billion from unauthorized trades. Today, Reuters reports that UBS shareholders have yet to file any class action lawsuits against the Swiss bank.

The lack of litigation is unusual because similar scandals typically result in plaintiffs lawyers rushing to file class actions on behalf of investors who allegedly were harmed.

According to Reuters, UBS shareholders in the U.S. will face hurdles if they do pursue litigation.

First, UBS has stated that no client money was involved in the alleged fraud.

Second, U.S. securities law says that damages can’t exceed the difference between the amount that shareholders paid for their shares and the average price of the company’s stock over a 90-day period beginning on the day the misleading information was made public, so if UBS stock rises, it would minimize possible damages.

Finally, the Supreme Court ruled in 2010 in Morrison v. National Australia Bank Ltd. that shareholders couldn’t bring claims for shares purchased on foreign exchanges. Only 12 percent of UBS shares are listed in the U.S., so the bank’s exposure to class action litigation brought by U.S. shareholders would be limited.