The constitutional question is whether any of these enumerated powers authorize Congress to require that individuals purchase health insurance or pay a fine. The only potential candidates are the power to tax and the power to regulate interstate commerce. Last year, to get the legislation passed, liberals denied that the fine is a tax and made sure that the law calls it a “penalty” and exempts those failing to pay it from the punishment that applies to tax evaders. But today, to defend the legislation in court, the Obama administration argues that the penalty is a tax after all. Judge Hudson called this disingenuous argument “a transparent afterthought” and no court has agreed with it; some have declined to address it at all.

The only enumerated power that anyone seriously argues can justify the insurance mandate is the power to regulate interstate commerce. The Constitution gives Congress the power to regulate interstate “commerce,” which the Supreme Court in 1824 defined in terms of commercial and related activity. In the 1930s, the Supreme Court expanded this category to include activities that substantially affect interstate commerce. Every commerce clause case ever decided by the Supreme Court, or by any federal appeals court for that matter, has involved an activity in which individuals chose to engage.

The Obamacare insurance mandate is not in this category at all. Rather than regulating activity in which individuals choose to engage, Obamacare regulates the decision itself. Rather than a person’s choice triggering the regulation, Obamacare make the choice for them. Even the first judge to uphold the insurance mandate called this “an issue of first impression” and distinguished between economic activity and economic decisions. Before Judge Hudson, the Obama administration argued that “economic decisions” are “economic actions” that can be regulated. Reacting to Judge Hudson’s ruling, Stephanie Cutter wrote on the White House blog that the law seeks to regulate “economic decision making.”

The trick is that the courts measure whether an activity affects commerce by looking not only at the individual challenging the regulation, but at the effect of everyone engaging in that activity. The Obama administration today makes the same argument for regulating everyone’s economic decisions. Every economic decision will, practically by definition, affect commerce if everyone makes it. That is a recipe for virtually unlimited federal power. If the federal government can require you to make certain economic decisions, including purchasing certain goods or services, what can’t the federal government do?

The Supreme Court ultimately will decide whether the federal government may regulate not only interstate commerce (what the Constitution allows), or activities that substantially affect interstate commerce (what the Supreme Court allows), but all economic decisions by individuals (what the Obama administration wants). Judge Hudson correctly concluded that “an individual’s personal decision to purchase-or decline to purchase-health insurance from a private provider is beyond the historical reach of the Commerce Clause.”

Any other conclusion requires treating the Constitution as the servant, rather than the master, of Congress. If the Constitution means whatever Congress wants, then it is really no Constitution at all because it cannot impose any real limits, leaving the federal government to define its own powers. That will be the death of liberty.