Like hospitals?
If it's 100% private, and accepts zero federal, state, or local funds, I'd say yes. The overwhelming majority of people wouldn't turn a sick person away, regardless of their views on whatever criteria you want to use. But if a private hospital has treated a certain person on more than one occasion without being paid for services rendered, then they should have every right to send them kicking rocks. If physicians take the Hippocratic Oath and take it seriously, then there shouldn't be a problem anyway.
Not sure if "Duty to Rescue" laws would also apply to hospital staff.