VINSON’S MOST STRIKING ERROR…. In his ruling on the Affordable Care Act yesterday, Judge Roger Vinson made a variety of errors in fact and judgment, but there’s one point in particular that deserves a closer look. From the ruling:

“… the mere status of being without health insurance, in and of itself, has absolutely no impact whatsoever on interstate commerce (not ‘slight,’ ‘trivial,’ or ‘indirect,’ but no impact whatsoever) — at least not any more so than the status of being without any particular good or service. If impact on interstate commerce were to be expressed and calculated mathematically, the status of being uninsured would necessarily be represented by zero. Of course, any other figure multiplied by zero is also zero. Consequently, the impact must be zero, and of no effect on interstate commerce.”

This comes up quite a bit among opponents of the law on the right. The government has the power to regulate interstate commercial activity, including health insurance, but those who choose not to buy coverage aren’t engaging in an activity, and therefore fall outside the law’s reach.

It’s important to appreciate how mistaken Vinson is here.

The argument from the Obama administration is straightforward: the Commerce Clause empowers the federal government to regulate interstate commerce; the American health care system is interstate commerce; and the Affordable Care Act regulates the health care system. As such, the ACA fits comfortably within the confines of the Commerce Clause.

Yes, there may be folks who don’t want to buy insurance, who would be penalized under the law. But under our system, those folks still get sick, still go to the hospital with medical emergencies, and — here’s the kicker — still get care. As you may have noticed, for quite a while, it’s been one of the right’s favorite arguments: the uninsured can always just go the emergency room and receive treatment, whether they have insurance or not.

Of course, when the uninsured get this care, and can’t pay for it, the costs are passed on to the rest of us — it makes the entire system more expensive, with hospitals and medical professionals providing care without compensation from the patient. As a consequence, those who would choose not to get coverage have a significant impact on the larger health care system, which is precisely why the notion of a mandate enjoyed broad, bipartisan support up until late 2009. There was never any doubt as to its constitutionality; this was a no-brainer.

Indeed, the Constitution empowers the government to make laws that “shall be necessary and proper” to “regulate commerce among the several States.” ACA proponents say the mandate is necessary and proper to effectively regulate the marketplace; Vinson says the necessary and proper clause of the Constitution doesn’t really count.

To put it mildly, the judge and those heralding the ruling aren’t exactly making a persuasive case.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.