After the justices of the high court administered what the Wall Street Journal, in a marvelous editorial this morning, is calling a “constitutional awakening,” at least some legal experts will be watching for one of the most explosive names in constitutional law — Korematsu. That is the case in which the Supreme Court allowed Franklin Delano Roosevelt’s administration to force Japanese Americans into detention centers on the Coast. It did so without any allegation that the internees had done something wrong. Just by existing they got into trouble. Now, in scattered online postings, some legal scholars are suggesting that President Obama’s health care law involves the same constitutional problem.

Korematsu was named for an American from Oakland, Fred Korematsu, who failed to report to a detention center. Eventually the Supreme Court ruled against him six to three in a decision that is regarded as one of the worst ever made by the high court. Mr. Korematsu was later cleared by a lower court. But the Supreme Court precedent has never been reversed. Michael Greve, a legal scholar with the American Enterprise Institute at Washington, reckons that Korematsu could figure in the constitutional drama over Obamacare. For Korematsu, Mr. Greve says, is the only case he knows of in which the Supreme Court has vouchsafed a federal government action requiring citizens who had not engaged in any regulable conduct to nonetheless perform an affirmative duty.

What Mr. Greve stresses is the distinction between a prohibition and prescription, meaning an affirmative command. He calls the distinction “completely fundamental” in federal law and in the Constitution. He suggests that save for constitutionally specified exceptions such as military and jury duty, the American tradition at the federal level is prohibitive, relying on negative law, or prohibitions. So strong is the tradition that civil and military authorities bent over backwards to avoid issuing prescriptive orders against Japanese Americans. They did not want to require them even to report to detention centers. What they did was prohibit them from leaving a military district that included their homes and also from entering that district. Reporting to a detention center was the only way to comply with both orders.

In other words, they were trapped, the same way Americans without health insurance would be trapped under Obamacare. No one is suggesting the two cases are exactly comparable. Korematsu, although ostensibly about the president’s wartime powers, was riddled with the question of racism and civil rights. The Obamacare case, on the other hand, is not about civil rights and racism or wartime powers. It is about the reach of the federal government under the commerce clause and the taxing power. But it holds at least the possibility that the Nine will use the occasion not only to lift the shadow of Obamacare’s mandate but also to draw the firm, principled constitutional line they refused to draw in Korematsu.