The Supreme Court’s infamous 1944 Japanese internment decision, Korematsu v. United States, has never been overturned. But does that mean, as some of Donald J. Trump’s associates have recently implied, that it is still good law, a precedent that could be cited in support of a national registry for Muslim immigrants or other morally repugnant classification schemes?

The ultimate answer is no — but the no is not a simple one. The legal doctrine of stare decisis holds that precedent ordinarily remains in place until it is overturned. And cases that seemed outdated and disreputable but remained on the books have sometimes recurred in the court’s jurisprudence, particularly after the Sept. 11 attacks.

So a moral plea for the government not to treat Korematsu as law is not enough. Fortunately, there is also a legal argument for why Korematsu should not be treated as such.

The most straightforward way to reject Korematsu is to understand it not as the definitive word on the true meaning of the Constitution, but simply as a moment in historical time in which particular justices applied the law to specific facts. According to this view, a decision can be wrong at the very moment it was decided — and therefore should not be followed subsequently.