The Supreme Court on Oct. 4. (Manuel Balce Ceneta/AP)

Kenneth W. Starr served as U.S. solicitor general from 1989 to 1993 and U.S. Circuit judge for the District of Columbia Circuit from 1983 to 1989. He joined an amicus brief supporting summary reversal in the U.S. Supreme Court in the pending Bobby Moore case.

The job of a judge is to follow the law. If we are to be, as Chief Justice John Marshall wrote, “a government of laws, and not of men,” the lower courts must carefully apply the precedent of the Supreme Court. Unfortunately, the top criminal court in my home state of Texas is not following this foundational constitutional principle in a matter of life and death.

Last year, in a case involving a death row prisoner named Bobby Moore, the U.S. Supreme Court held that Texas’s framework for determining whether a capital defendant had an intellectual disability — and was therefore exempt from execution — violated the Eighth Amendment. The rejected Texas criteria had in some circles become known as “the Lennie standard” because it invited the courts to compare the defendant with the fictional character Lennie Small in “Of Mice and Men” — a giant man with the mind of a child.

With respect to Moore, the Supreme Court ruled that the Texas Court of Criminal Appeals wrongly relied on non-clinical criteria about intellectual disability to uphold his death sentence. Three justices dissented from the court’s reversal. But as all justices agree, the Supreme Court’s majority decision is the law of the land. And all justices unanimously agreed that the Texas’s use of lay stereotypes was erroneous and unconstitutional.

The Supreme Court’s majority opinion emphasized that, as a 13-year-old, Moore lacked a basic understanding of the days of the week, the months of the year, telling time, the seasons and the concept that subtraction is the reverse of addition. Stressing that Moore’s serious mental and social difficulties were clear from early childhood, the court highlighted what it called “the considerable objective evidence of Moore’s adaptive deficits.” The majority also held that Moore’s IQ is well within the range of intellectual disability, an issue that is no longer in dispute. As is customary, the Supreme Court then sent the case back to the Texas court for further proceedings.

If the system were working as it should, Moore’s case would have been a routine matter of the Texas court applying the Supreme Court’s decision and current medical standards as directed and prohibiting Moore’s execution. Even the prosecutors, who had obtained the death penalty against Moore, agreed in a formal filing to the Texas court that, in light of the controlling medical and legal standards, Moore is intellectually disabled and should not be executed.

Yet in a stark conflict with black letter law, the state appellate court again ruled that Moore is not intellectually disabled and set him on course for execution. The decision made reference to the Supreme Court’s ruling, but for the second time relied on lay stereotypes and non-clinical criteria despite the Supreme Court’s explicit instructions.

While I have no doubt about the good faith of the esteemed judges in Texas, their decision deviates sharply from the Supreme Court’s prior decision. The Supreme Court justices should again accept review of Moore’s case and summarily reverse this latest ruling. The Texas court, in reaching its closely divided decision, rejected the consensus of the highest court in the country, the state trial judge who held the evidentiary hearing and all parties and amici before the court — including the prosecutors, prominent Texans concerned with the rule of law and leading medical organizations.

Reasonable minds can differ about the death penalty. Some urging the Supreme Court to take up Moore’s case again support capital punishment, and some oppose it. But these citizens supporting Moore, including leading conservatives, are committed to upholding the Constitution, which established “one Supreme Court.” In giving the court the last word, the framers intended that the Constitution would be applied consistently, without exceptions and regardless of the status of a particular litigant.

I am not an abolitionist on the death penalty. I favor it in appropriate cases. But I also believe we must vigilantly observe the constitutional constraints on this ultimate sentence. In our constitutional system, courts must carefully adhere to Supreme Court decisions on all issues — especially on this vitally important subject of life and death.

In this instance, a narrow majority of Texas judges may have believed that the Supreme Court was wrong about Moore. But this does not matter, as I know from my own experience as an appellate judge. The state judges had an inviolable duty to ensure that its proceedings were consistent with the court’s decision. As then-U.S. Court of Appeals for the District of Columbia Circuit Judge Brett M. Kavanaugh put it: “As a lower court in a system of absolute vertical stare decisis headed by one Supreme Court, it is essential that we follow both the words and the music of Supreme Court decisions.”

For our system to work, the Supreme Court must make sure that its rulings are respected and faithfully applied. In this case, I hope the Supreme Court will act to correct the Texas court’s fundamental error, especially since Moore faces the most extreme punishment our government can impose. Ignoring this departure from binding authority would be inimical to our bedrock constitutional principles.