Last week, when crack Reuters journalist Jon Stempel wrote a story about the obstacles Olympus common shareholders would face if they filed a U.S. securities fraud class action, he reported that the U.S. Supreme Court's infamous 2010 opinion in Morrison v. National Australia Bank, which has been widely interpreted as a bar on securities claims for foreign-traded shares, probably wouldn't preclude claims by investors in Olympus American Depository Shares, which trade over the counter on the Pink Sheets. But Olympus's ADR float, Stempel said, is only about 1 percent of its market capitalization. "No institutional investor owned even as much as $1 million of the ADRs as of [last week], according to BNY Mellon Depository Receipts," Stempel's story reported. "This makes it unlikely that ADR investors could collectively seek a big recovery by suing."

Unlikely, but not impossible. As Kevin LaCroix at D&O Diary was the first to report, three law firms have filed a Philadelphia federal court class action accusing Olympus of securities fraud. The complaint cites the apology Olympus posted on its own website, which admitted that the company "had been engaged in activities such as deferring the posting of losses on investment securities."

I asked one of the plaintiffs' lawyers, Kenneth Vianale of Vianale & Vianale, if he had big expectations for the case. He readily conceded that damages will likely be limited because the ADR float just isn't that big. "I don't think it's a big class," he said. "We're not expecting super damages."

But Vianale said there didn't seem to be any point in trying to include common stockholders who bought Olympus shares overseas, thanks to Morrison. "You can't really get past that case," he told me. "Rulings over the last year basically put to rest any creative ideas to get around it."

The other firms on the ADR complaint are Serraf Gentile and Greenfogel & Skirnick.

(Reporting by Alison Frankel)