Although there are solid arguments and precedents that an individual mandate in the Patient Protection and Affordable Health Care Act (PPCA) is well within the four corners of the Constitution, it is also worth noting that the supposed demonic imperative that a person must actually purchase an insurance plan from a private company does not even exist.
If a person prefers not to purchase health insurance, he pays a fine. The choice is purely voluntary. That fine does not require any purchase of any private product. In no case is anyone compelled to have any medical care at all.
All it does is provide a pool of money to pay for uninsured peoples' medical care, rather than the mandate that currently exists in law and in fact that the rest of us who pay premiums or pay directly for our health care pick up their tab in the form of higher prices. It does what a tax does, but it differs because it offers people the alternative of purchasing health insurance.
In 1986 Congress passed the Federal Emergency Medical Treatment and Labor Act (EMTALA), which guarantees people who need emergency care or are in labor the medical care they need before they can be transferred or discharged. Cases under the act have gone to the Supreme Court, which has interpreted its provisions (e.g., what is the minimum care required?), but never suggested that it was unconstitutional. That law in effect imposes a mandate on emergency rooms that is passed along to others in the form of higher premiums or higher direct costs.
Thus, what the PPCA actually does is eliminate the current mandate that the insured assume those costs in favor of a choice between a fine and purchasing insurance.
Conceptually, under the PPCA everyone pays for our health-care system in the form of a fine. They can avoid paying that fine by purchasing insurance, which also pays for our health-care system. Each person can choose for himself.
It is two sides of the same coin, but it looks at the fine-side first.