Few legal cases in the modern era are as consequential, or as defining, as the challenges to the Patient Protection and Affordable Care Act that the Supreme Court hears beginning Monday. The powers that the Obama Administration is claiming change the structure of the American government as it has existed for 225 years. Thus has the health-care law provoked an unprecedented and unnecessary constitutional showdown that endangers individual liberty.

It is a remarkable moment. The High Court has scheduled the longest oral arguments in nearly a half-century: five and a half hours, spread over three days. Yet Democrats, the liberal legal establishment and the press corps spent most of 2010 and 2011 deriding the government of limited and enumerated powers of Article I as a quaint artifact of the 18th century. Now even President Obama and his staff seem to grasp their constitutional gamble.

The Supreme Court will not be ruling about matters of partisan conviction, or the President's re-election campaign, or even about health care at all. The lawsuit filed by 26 states and the National Federation of Independent Business is about the outer boundaries of federal power and the architecture of the U.S. political system.