The legal basis for rescission is that when you sign an insurance application, you are warranting that the information on the application is true; if it turns out not to be true, the insurer can get out of your insurance contract. It’s particularly nasty in practice because the insurer does not immediately investigate your application to determine if it is accurate before selling you the policy (that would be impractically expensive); instead, the insurer waits – years, in many cases – until you actually need expensive health care, and then does the investigation, which at that point is worth it because of the payments the insurer could potentially avoid. Also, you can lose your coverage for innocent mistakes, which are easy to make since the application form asks you if you have ever seen a doctor for any one of a long list of medical conditions that you are certain not to recognize or understand. (In a Congressional hearing, the CEO of a health insurer admitted that he did not know what several of the conditions listed on his company’s application were.)