“If the government can do this, what, what else can it not do?” asked Supreme Court Justice Antonin Scalia this week in arguments on the constitutionality of the requirement that nearly all Americans buy health care insurance or face a penalty.


“All bets are off,” Chief Justice John G. Roberts Jr. gravely added.


Thus did this week’s Supreme Court arguments over the Obama administration’s health care law emerge as a historic test of federal power versus individual liberty, all the more remarkable given that just a few weeks ago, the overwhelming view of constitutional scholars was that this wouldn’t be a close case, with even conservative justices likely to uphold the law.


That it now looks not only possible but perhaps likely that the Supreme Court will strike down the health care law as unconstitutional, probably in its entirety, is a tribute to some skilled and passionate advocacy and the persuasive power of conservative media — and what seems a breathtaking departure from decades of Supreme Court jurisprudence.


It’s always hazardous to predict a Supreme Court outcome, no matter how pointed the questioning at oral argument. This seems especially true when the legal debate over health care has become so intensely politicized. Picketers were marching around the Supreme Court building. By their questioning, the four conservative Republican appointees seemed to signal their distaste for the law, while the four liberal Democratic appointees seemed to embrace it. That left Justice Anthony M. Kennedy in his usual position as the swing vote, and he asked some tough questions, at one point suggesting the government faced “a heavy burden of justification.”


While the health care law has generated intense passions on both sides, I don’t share them. Although it seems well established that many Americans are burdened with costly and yet woefully ineffective health care, if I’d been elected president, I probably would have focused my attention on the financial crisis and the economy and moved more slowly on health care reform. But I’m no expert on the byzantine subject that has confounded more than one administration, and as far as I can tell, the legislation has had no effect on me, my family members or friends, all of us fortunate enough to have adequate health coverage.


But limiting Congress’s power to legislate under the commerce clause is another matter, and could have far-reaching, and unintended, consequences beyond health care. Despite the often opaque and convoluted arguments this week, the legal issues don’t strike me as all that complicated. No one disputes that Congress can enact laws to carry out powers enumerated in the Constitution or necessary and proper to effectuate those powers. Among the enumerated powers: “To regulate Commerce with foreign Nations, and among the several States, and with the Indian Tribes.”


As the nation’s economy evolved from largely local markets to regional, national and increasingly global ones, the Supreme Court has taken a progressively broader view of Congressional power under the commerce clause, even when individual freedom had to be sacrificed. This included limiting one farmer’s ability to plant wheat during the Depression because his production affected the overall supply and hence had an effect on interstate commerce; and, more recently, upholding a federal ban on homegrown marijuana even if the plant never crossed state lines. The court has stressed that Congress needs only a “rational basis” for concluding that economic activity might affect interstate commerce, and even Justice Kennedy’s somewhat stricter standard of a “tangible link to commerce” based on “empirical demonstration” seems readily met here.


With famed hospitals like the Cleveland Clinic mounting national ad campaigns and health insurers operating in national markets, there would seem to be little argument that health care affects interstate commerce, and that one person’s decision to buy or not buy insurance, just like one farmer’s decision to plant wheat, would affect a national market. Congress has estimated that health care services and insurance account for 17 percent of the gross domestic product and amounts to more than $2 trillion annually.


But constitutional opponents of the law have seized on the mandate requiring most people to buy health insurance or face a penalty as an unconstitutional infringement of individual liberty. They’ve argued that a ban on individual activity that, magnified in the aggregate, might affect interstate commerce (like wheat farming), is fundamentally different from requiring someone to do something or face a penalty, as the health care legislation does. A lower court judge ruled that “inactivity”— the failure to buy health insurance — by its very nature cannot affect interstate commerce.