And here are the federal regulations

The FDA classified electronic cigarettes as drug delivery devices and subject to regulation under the Food, Drug, and Cosmetic Act (FDCA) before importation and sale in the United States. The classification was challenged in court, and overruled in January 2010 by Federal District Court Judge Richard J. Leon, citing that "the devices should be regulated as tobacco products rather than drug or medical products."[31][32]

In March 2010, the U.S. Court of Appeals for the District of Columbia stayed the injunction pending an appeal, during which the FDA argued the right to regulate electronic cigarettes based on their previous ability to regulate nicotine replacement therapies such as nicotine gum or patches. Further, the agency argued that tobacco legislation enacted the previous year "expressly excludes from the definition of 'tobacco product' any article that is a drug, device or combination product under the FDCA, and provides that such articles shall be subject to regulation under the pre-existing FDCA provisions."[33] On 7 December 2010, the appeals court ruled against the FDA in a 3–0 unanimous decision, ruling the FDA can only regulate electronic cigarettes as tobacco products, and thus cannot block their import.[34] The judges ruled that such devices would only be subject to drug legislation if they are marketed for therapeutic use – E-cigarette manufacturers had successfully proven that their products were targeted at smokers and not at those seeking to quit. The District Columbia Circuit appeals court, on 24 January 2011, declined to review the decision en banc, blocking the products from FDA regulation as medical devices.[35]

In April 2014, the FDA proposed new regulations for tobacco products, including electronic cigarettes. The regulations require disclosure of ingredients used in e-cigarette liquids, proof of safety of those ingredients, and regulation of the devices used to vaporize and deliver the liquid.[36][37][38][39]