Federal Powers: Where in the U.S. Constitution does it say the government can force people to buy health insurance? And by what authority does it prohibit the purchasing of insurance across state lines?A key part of the administration's plan to reform health care is what is called the "individual mandate" — a requirement that everyone must have health insurance either through his or her employer or purchased individually. A good chunk of the uninsured are that way of their own volition. They are young and healthy and feel they have better things to do with their money at this point...