In 2004, Congress told the FDA that it had until 2008 to set a definition for what "gluten-free" means. It never did, allowing food makers to market products that may contain some gluten as safe for those with Celiac disease. From the Washington Post:

"The FDA has spent years calling upon experts to have open-forum debates, town hall meetings - we've been having reiteration and reiteration," said Alessio Fasano, medical director of the Center for Celiac Research at the University of Maryland School of Medicine. "They've been reiterating and listening to Grandma, Grandpa, people on the street corners. . . . I really don't understand why it's lingering up in the air when it really should be a no-brainer."

Let's give the FDA an incentive. If they don't figure it soon, we'll send Elisabeth Hasselbeck to explain it to them.

3 Years After Deadline, FDA Still Hasn't Defined ‘Gluten-Free' [Washington Post]