Only a few months ago, the White House and its allies on the legal left dismissed the constitutional challenges to ObamaCare as frivolous, futile and politically motived. So much for that. Yesterday, a federal district court judge in Virginia ruled that the health law breaches the Constitution's limits on government power.

In a careful 42-page ruling, Judge Henry Hudson declared that ObamaCare's core enforcement mechanism known as the individual mandate—the regulation that requires everyone to purchase health insurance or else pay a penalty—exceeds Congress's authority to regulate the lives of Americans.

"The unchecked expansion of congressional power to the limits suggested by the Minimum Essential Coverage Provision [the individual mandate] would invite unbridled exercise of federal police powers," Judge Hudson writes. "At its core, this dispute is not simply about regulating the business of insurance—or crafting a scheme of universal health insurance coverage—it's about an individual's right to choose to participate."

So the issue is joined, and no doubt with historic consequences for American liberty. For most of the last century, the U.S. Supreme Court interpreted the Constitution's Commerce Clause as so elastic as to allow any regulation desired by a Congressional majority. Only with the William Rehnquist Court did the Justices begin to rediscover that the Commerce Clause has some limits, as in the Lopez (1995) and Morrison (2000) cases.

The courts up through the Supremes will now decide if government can order individuals to buy a private product or be penalized for not doing so. If government can punish citizens for in essence doing nothing, then what is left of the core Constitutional principle of limited and enumerated government powers?