Per D103's comment, the power that exists that is greater than the FDA are the US Courts, which have already ruled against the FDA's attempt to ban e-cigarettes by classifying them as unapproved drug devices.
Although the news media hasn't picked up on this yet, it was Sharfstein who organized the FDA's July 22, 2009 press conference (that was originally scheduled for May 5, but was postponed after I urged the FDA to do so) where he knowingly and intentionally misrepresented the health risks/benefits of e-cigarettes, misrepresented the FDA's own laboratory test to claim the products had toxic chemicals (i.e. diethylene glycol) and carcinogens (even though they were at similar levels to those in NRT), and invited other speakers to falsely claim that (flavored) e-cigarettes were target marketed to children.
I also strongly suspect that Sharfstein has been the leading proponent at FDA to continue appealing ad nauseum the e-cigarette litigation filed by SE/NJOY, which may have been a reason (and perhaps the key reason) for his departure from the agency.