This is the intriguing question asked in a Christian Science Monitor op/ed by Loyola Law School professor Karl Manheim and Consumer Watchdog chairman Jamie Court. To wit:
The federal government does not ordinarily require Americans to purchase particular goods or services from private parties.
The closest we come is when government imposes a condition on the grant of discretionary benefit or permit. For instance, in most states, you must have auto insurance to drive a car, or you are required to install fire sprinklers when building a new house. But in such cases, the "mandate" is discretionary – you don't have to drive a car or build a house. Nor do you have a constitutional right to do so….
A health insurance mandate is essentially a forced contract, in which one party (the insurer) gets to set the terms. You must buy their policies, even if you prefer to self-insure, rely on alternative medicine, or obtain treatment outside the system. In constitutional terms, such mandates may constitute a violation of due process or a "taking of property."
Requiring Person A to give money to Person B is a "taking," whether or not something of value is given in return. Let's say the state required every resident to buy milk, on the rationale that milk consumption benefits public health. That's either a constitutionally forbidden taking (of money) or a violation of due process.
These constitutional rights aren't absolute. Given a compelling enough reason, government can interfere with your person and property. It can require, for instance, that your child be vaccinated before attending public school. But there is usually an opt-out, such as private or home schooling.
We are not aware of any opt-outs for most people in the mandatory health insurance plans being discussed.
Manheim and Court suggest that a tax-financed single payer government health insurance scheme would meet constitutional muster.
Whole op/ed here.
My arguments (admittedly without any constitutional analysis) for mandatory private health insurance here.
I find it a bit ironic that an op/ed on health insurance appears in the Christian Science Monitor.