Is Affordable Care Act Constitutional?

Does Congress possess the constitutional power to force its citizens to purchase health insurance?  Prof. Elizabeth Price Foley says that’s the key question in the Supreme Court challenge to the Patient Protection and Affordable Care Act. The Supreme Court must decide whether the “individual mandate” portion of the law falls under Congress’s power to “regulate commerce,” as enumerated by Article 1, Section 8 of the Constitution. Prof. Foley argues that whether or not you personally support the health care legislation, you should be worried about the precedent that the individual mandate would set. If the power to regulate commerce is interpreted as including the power to force people to buy something, then that power doesn’t just apply to health care. It would give Congress the power to make individuals buy anything, which poses a significant threat to individual liberty.
Prof. Foley worked with the Institute of Justice to submit an amicus brief on the case, arguing that the individual mandate is like forcing a contract. Yet for hundreds of years, contracts have been understood as voluntary agreements between two parties. Thus, a forced contract is a contradiction in terms, and therefore unlikely to have been the kind of power intended to fall within the power to “regulate commerce.”
Prof. Foley worked with the Institute of Justice to file an amicus brief on the case: http://www.ij.org/health-insurance-reform-a-the-supreme-court