A couple years back, securities class action plaintiffs in the Lehman litigation advanced an intriguing theory. The credit rating agencies, they argued, weren’t mere evaluators of certain Lehman mortgage-backed securities, but were actually so involved in structuring the securities–and supplied ratings so crucial to the offering–that the rating agencies were, in effect, underwriters. It was a novel argument that seemed to offer securities class action plaintiffs a way to pierce the First Amendment armor protecting the rating agencies.

And so far, it’s been completely unsuccessful. On Wednesday, Manhattan federal district court judge Harold Baer became the fourth judge in the Southern District to dismiss a class action asserting underwriter liability against the rating agencies, ruling in a 17-page opinion that investors led by the Public Employees Retirement System of Mississippi cannot pursue Securities Act claims against Standard & Poor, Moody’s, and Fitch for their role in a Goldman Sach offering of mortgage-backed pass-through certificates.