The FDA would have a difficult time justifying creation of regulations on the sale or consumption of caffeine at this point. For the FDA to establish regulations regarding products containing caffeine, the agency would have to reverse itself on a long-standing policy. In 1978, the FDA reviewed caffeine carefully, and issued a position statement regarding its conclusion. You can read the position paper at this link. In essence, the FDA found caffeine suitable for inclusion on the GRAS (Generally Regarded As Safe) list, a list of substances that have been in use for a long period of time and have been found to be of low or no concern from a public health standpoint. In the case of caffeine, it has a very long history of use in food and beverages. There is no scientific proof that caffeine causes any long-term health damage in humans; awhile a few studies have shown caffeine-related negative effects in rodents, the dosages needed to effect these problems are so great as to be unreasonable when scaled up to the level of human consumption.