Last year, the US Supreme Court held that a cause of action against a manufacturer of generic drugs is preempted if the claim is based on the manufacturer's failure to update or strengthen its warnings unless the manufacturer of the same brand name drug was obligated to do it. Go here for details on this decision and go here and scroll down for much more on the background before the case was decided and links to much more information since the case was decided. (I thnk the first post on this subject is on Nov 2, 2010).
Since then, a series of legal challenges have been filed, but all have been rejected. Today Pharmalot is reporting on the most recent example. The FDA Law Blog has also posted a good summary of the state of the law.