The Supreme Court just ruled that at least some federal prisoners who are completely innocent must serve out their entire sentence, with no meaningful way to challenge their unlawful conviction.

One of the most fundamental principles of criminal law is that no one may be convicted of a crime unless the legislature previously passed a law making their actions illegal. If there is no law on the books that, say, marijuana possession is unlawful, then a judge cannot toss someone in jail because they were found with a joint.

The Supreme Court’s 6-3 decision in Jones v. Hendrix, handed down Thursday, does not directly attack this foundational principle. Instead, it does so indirectly by prohibiting many prisoners from ever challenging their convictions in court.

The case centers on Marcus DeAngelo Jones, a federal prisoner who was convicted in 2000 of possessing a firearm after being convicted of a felony. Nineteen years […]