AMENDMENT XXVIII (proposed)
The right of citizens of the United States shall not be denied or abridged by the United States or by any State on account of any medical condition. Citizens of the United States and their dependents shall not be given any medicine without their express permission.
(1st edit to include definition of medicine) Medicine includes diagnostics and anything related to the prevention and treatment of injury or disease.
(2nd edit to include dependents)
Hard to envision how evil they might be. Or, how to find a loop hole, as you say. Is flouride in the water medicine? Is adding gas (or other chemicals to the air) medicine? Do we need to enumerate the methods? (oral, injection, suppository, ointment, inhalation, etc.)