People who commit to buy a stock on Day 1 can't complain about misrepresentations that the stock issuer made on Day 2 or later. E.g., APA Excelsior III L.P. v. Premiere Techs., Inc., 476 F.3d 1261, 1267 (11th Cir. 2007). The later lies could not have induced you to buy the shares, the theory goes.

But what if you agree to vote your Company A shares in favor of a deal that, if it goes through, will require you to buy shares in Company B after Company A merged into it?

The Ninth Circuit ruled on Monday that the share owner could sue the issuer of Company B, under section 11 of the Securities Act of 1933, for inflating Company B's income and lowballing its costs, by $120 million and $190 million, respectively. The panel held that a voting agreement that mandated a shareholder to favor a merger between Companies A and B did not make the shareholder "irrevocably bound to exchange his Harbinger shares for Peregrine stock at the time the [false] Registration Statement was filed." Hildes v. Arthur Andersen LLP., No. 11-56592, slip op. 14 (9th Cir. Aug. 19, 2013). Sure, he had to vote for the merger, but he didn't make a deal he had to keep no matter what. But-for the falsities in the Registration Statement, the court concluded, the merger would not have happened, and the shareholder could have walked away from the transaction. That made the district court's dismissal of the case improper.