Still, Fidelity and TD Ameritrade were in the same position as Schwab: They weren’t underwriters, yet they settled. So what makes Schwab special?

“It is impossible for us to comment on the reasons other firms chose to settle,” a Schwab spokesman says. “We don’t know, for example, how they marketed or promoted the products or what other circumstances may have influenced their decisions.”

However, Charles Schwab himself may provide an answer. In a sharply worded op-ed piece in the Wall Street Journal two days after the New York lawsuit was filed in mid-August, he stormed that such legal actions would essentially destroy his business model of offering low-cost brokerage-only services—sans advice. “The issue at stake here is whether independent investors should be allowed the freedom to choose what they are allowed to buy, sell, or hold,” he wrote. “Forcing them to pay an advisory fee would be a significant new cost to them, and the fees would likely shut many small investors out of the capital markets altogether.”

Of course, Schwab could just be posturing in hopes of bargaining for better terms—hardly an unheard-of tactic in lawsuits. But Constance Wagner, an associate professor at St. Louis University School of Law, says the op-ed raises the stakes. “It seems to me that it’s a point of principle to him,” she says. “It’s definitely an economic issue as well.”

She also points out that the Martin Act gives the attorney general some pretty strong ammunition. “That is perhaps why these other banks decided they want to settle,” she says.

The law can give an attorney general ammunition outside the courtroom as well. New Yorkers might remember another recent attorney general who filed Martin Act lawsuits against big financial firms, got the firms to settle, and then parlayed that dragon-slaying popularity into a successful campaign for governor.