RALEIGH – When federal judge Henry Hudson ruled Monday that the central feature of ObamaCare was unconstitutional, he wasn’t legislating from the bench or inserting himself into a policy debate about health care. He was applying a basic concept of constitutional interpretation: if you define a constitutional provision so broadly that it loses all meaning, you’re probably made an error.

Hudson struck down the legislation’s requirement that virtually all Americans purchase a government-approved health insurance policy. Without the individual mandate, the rest of the bill becomes problematic. It relies on overcharging some consumers to subsidize others, and on the mandate to deter people from gaming the system by waiting until they are sick before purchasing insurance.

In his decision, Hudson agreed with the argument of Virginia Attorney General Ken Cuccinelli that Congress lacks the constitutional authority to compel the purchase of a consumer product – in this case, an insurance policy. The U.S. Constitution does grant Congress the authority to regulate interstate commerce. But the original meaning of that provision was to prohibit state barriers to internal trade, not to give Congress unbridled authority to regulate virtually every private decision.

The Obama administration argued that the Commerce Clause allows Congress to compel the purchase of health insurance because a decision not to purchase it has the potential to affect the finances of hospitals, doctors, insurers, and other consumers – and thus to affect interstate commerce. Judge Hudson embraced precisely the correct rejoinder to this superficially plausible argument: is there anything that Congress couldn’t regulate by this definition?

He wrote that “the same reasoning could apply to transportation, housing, or nutritional decisions.” All consumer decisions can theoretically affect the decisions and expenditures of other parties. If the test is that even a decision not to consume has sufficient economic effects to trigger federal regulation via the Commerce Clause, pretty much all bets would be off.

For some progressives, of course, defining the Commerce Clause so expansively doesn’t sound as scary as it does to the rest of us. They’ve been trying for more than a century to reinterpret the constitution to remove what they perceive as its archaic limits on federal power. Sure, they might countenance carving out a few exceptions, based on concocted penumbras and their own personal preferences, but in their minds the presumption lies with government’s authority to intrude on private matters, not with individual freedom from such intrusion.

To define the Commerce Clause as opening the door to federal regulation of any economic decision that might have an effect on commerce, including a decision not to engage in commerce, is to delimit the limit. If politicians or judges find themselves redefining a constitutional limit to such a degree that virtually nothing lies inside it, they need to start over. They are making a basic error.

Consider the example of the Fourth Amendment. It states that “[the] right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated.” What if politicians or courts concluded that any search or seizure would be considered reasonable as long as law enforcement stated it was reasonable? Surely most police officers and prosecutors act in good faith. They are trying to discharge their responsibility to protect the public. Shouldn’t it be sufficient to accept their claim that their actions are reasonable?

Of course not. Even if one was inclined to trust law enforcement in most cases, such an interpretation would render the Fourth Amendment protection meaningless. Lawmakers and judges have to interpret “unreasonable” in some fashion that would actually preclude some searches or seizures.

Similarly, lawmakers and judges can’t accept interpretations of the Commerce Clause or other constitutional delegations of power that serve to remove federal constraints on congressional action. That would render unnecessary the very existence of a list of delegated powers in the first place.

Judge Henry Hudson has done his job, at least with regard to the chief issue in dispute. Now, advocates of individual liberty, constitutional government, and real health care reform can only hope the federal appeals courts do their jobs, too.

Hood is president of the John Locke Foundation.