They cancel you by not giving you the option to re-enroll.  Most plans have yearly enrollments.  At that time, the insurance companies can choose not to take you back as a customer.  So if you get diagnosed with an illness in May.  When you go to re-enroll in October, the insurance companies can drop you. Because it is 
legal for companies to deny coverage to those with pre-existing conditions, if you try to go to a different insurance plan, after being dropped by your original plan, you will be denied coverage or at best get offered a lessor plan that is 4 to 5 times higher than your original plan.
Surely a smart guy like you knows all of this.  Surely you know that lawyers can't change the law....
