This logic should be comforting to plan sponsors, given that ERISA requires sponsors to provide a summary plan document that is understandable and readable, Komornicka says. It would be difficult to create a summary that outlined every provision of the plan, yet remained easy to read. "The plan document stands on its own," she adds.

If all the justices had stopped there, the case essentially would have been over. However, six justices went on to say that § 502(a)(3) of ERISA, which provides for equitable relief to "redress violations of ERISA," could apply. What's more, the Supreme Court's opinion says that this could include monetary relief for losses resulting from a trustee's breach of duty.

The Court views reforming the plan under § 502(a)(3) is an "extraordinary remedy," Vaughan says, and one to be reserved for cases involving fraudulent actions, she adds. Indeed, "The District Court also found that Cigna intentionally misled its employees," the Supreme Court states.

The six judges also said that the participants in the plan didn't need to show that they relied on the information contained within the summary plan document, and then made a decision that later proved to be detrimental. However, the participants do need to show that they were harmed. "That means there's a greater likelihood of class action lawsuits based on ERISA;" Komornicka notes. Without this, plaintiffs in class-action ERISA suits would have to show that everyone in the class both read the description and relied on it -- either of which would be difficult to prove.