1. Once an addict, always an addict. That is how it's taught in rehab.
2. There are exeptions under federal law whereby the government can sidestep HIPAA privacy and obtain medical information. Examples of this are when guns and drugs mix or the VA will reporting a suicidal veteran who owns guns.
3. It is not illegal for a doctor to prescribe a drug that someone has been addicted to in the past. Someone injured in an auto accident will not be denied pain medications due to a past addiction. The doctor must act in the interest of the patient and medical necessity. Each state is different but similar in their laws.