There is no constitutional problem with Congress requiring that individuals purchase health care or pay a penalty. There is much to debate over health care reform and how to achieve it, but I have no doubt that the proposals would be constitutional.

The constitutional objection that I have heard most often is that Congress lacks the authority under Article I of the Constitution to do this. But such a mandate clearly falls within the scope of Congress's authority to regulate commerce among the states.

Over many cases, the Supreme Court has held that Congress can regulate economic activities that taken cumulatively across the country have a substantial effect on interstate commerce. Purchasing health insurance is an economic transaction. Taken cumulatively those who do this, or who don't do it, have a substantial effect on interstate commerce.

In 2007, healthcare expenditures amounted to $2.2 trillion, or $7,421 a person, and accounted for 16.2% of the gross domestic product. These statistics leave no doubt that regulating health insurance is regulating interstate commerce.

Those who argue that this is unconstitutional maintain that those not purchasing health insurance, by definition, are not part of interstate commerce. There are numerous flaws with this argument. First, Congress can regulate activities that themselves are not part of interstate commerce if they have a substantial effect on interstate commerce. For example, in Wickard v. Filburn, the Supreme Court held that Congress could regulate wheat that farmers grew for their own home consumption. More recently in Gonzales v. Raich, the Court ruled that Congress could prohibit cultivating and possessing small amounts of marijuana for personal medicinal use. Even though the individuals were not personally engaged in commerce, the matter still fit within the commerce power.

Second, not engaging in economic transactions is a form of commercial behavior that Congress can regulate. The Supreme Court held that Congress could require that hotels and restaurants provide services to African-Americans. Their refusal to engage in commerce still was deemed to be within the scope of Congress's commerce clause power.

Third, the likelihood is that everyone will require medical care at some point. An uninsured person in an automobile accident will be taken to the emergency room for treatment. An uninsured person with a communicable disease will be treated. Congress can ensure that there is an adequate fund to pay for everyone's medical needs.

In other words, the health care system is part of interstate commerce. Providing care for all unquestionably has a substantial economic effect. Congress, then, can use its authority under the necessary and proper clause to make sure that the system that it is creating is viable and capable of providing health care for all.

Nor is there any individual right violated by a mandate for purchasing health care. There is no constitutionally protected freedom to be able to refuse to be insured or to avoid paying for the benefits provided.

There are many close constitutional questions. But this is not among them. Congress clearly has the legal authority to require individuals to have health insurance.

Prof. Erwin Chemerinsky