Nicotine isn't regulated by what form it takes, but instead by "intended use" in the US.
If the nicotine is contained in a product with an "intended use" as a smoking cessation or other treatment, it is then regulated as a "drug" and must go through clinical trials, studies, etc., and the product must meet strict manufacturing protocols before release to the public. If the nicotine is contained in a product with an intended use of "recreational" (ie. intended for human consumption but not as a treatment of any kind) it is regulated as a tobacco product. (A third classification is a pesticide, but that form of nicotine is not allowed for human consumption.)
It was this "intended use" criteria which kept the FDA from being able to deem non-therapeutic e-cigarettes as unapproved drugs. So long as the manufacturer/retailer made no treatment/health/therapeutic claims, they weren't considered a drug, but that meant the only other option was "tobacco product." The FDA defines a "tobacco product" as any product that not only contains tobacco leaf, but also any derivative (ie. "a compound derived or obtained from another and containing essential elements of the parent substance") of tobacco. Nicotine is clearly a "derivative" of tobacco. While it is also a derivative of other plants, the nicotine in e-liquid is currently all derived from tobacco. However, since nicotine is classified by "intended use" and not the source, even nicotine from other plant material could be deemed a substantial equivalent and treated exactly the same as tobacco-derived nicotine, because of it's intended use. It's obvious to everyone that we use e-cigarettes with the same "intended use" as other tobacco products - mainly, the same way we used to use traditional cigarettes. It may be a far safer form of recreational nicotine use that regulators never foresaw, but it is still technically "recreational use" of nicotine derived from tobacco.
It's important to note that the only "bad" things about being considered a tobacco product is 1) the public perception that all tobacco products are equally harmful and 2) the threat that the FDA will regulate them as if all tobacco is equally harmful. Educating the public and correcting this perception and convincing the FDA and politicians not to regulate low-risk tobacco products identically to high-risk products is CASAA's goal. Changing perceptions and exposing the lie that there "is no safe tobacco product" will also go a long way towards gaining social acceptance. (ie. If the public still believes that all nicotine use should be discouraged because it's equally dangerous, it won't matter if e-liquid gets a separate category. They will just regulate that category as strictly as tobacco - possibly worse. We could end up with less hoops to jump through than drug products, but far more than if we are a tobacco product.) The chance that the FDA will treat a product that is derived from tobacco and used like tobacco as a whole separate category, with less rules than tobacco, is extremely slim. Especially if the public continues to believe that the ultimate goal in smoking cessation is eliminating the nicotine addiction instead of eliminating exposure to smoke.