Krystle Campbell, Lingzi Lu, and Martin Richard were murdered in cold blood when Dzhokhar Tsarnaev and his brother, Tamerlan, detonated two pressure-cooker bombs at the Boston Marathon finish line in 2013. In the “battlefield-like carnage” that followed, the federal appeals court in Boston later recounted, “blood and body parts were everywhere” and the “smell of smoke and burnt flesh filled the air.” Hundreds of bystanders were injured. Many were maimed for life. Three days later, Tsarnaev and his brother gunned down MIT police officer Sean Collier. Then they engaged in a shootout with police in Watertown, severely wounding two officers; one of them, Dennis Simmonds, later died from his injuries. While trying to escape in a stolen car, Dzhokhar ran over his brother and killed him too.

It was the deadliest terrorist attack in Boston history, and after Tsarnaev was indicted, polls showed the overwhelming majority of Americans believed he should be executed if found guilty. The Obama administration agreed. When Tsarnaev was prosecuted in federal court, the government successfully sought the death penalty. And when the First Circuit Court of Appeals in 2021 overturned that sentence on procedural grounds, the federal government under President Biden urged the Supreme Court, again successfully, to reinstate it.

Now Biden is being asked to do by means of presidential clemency what his administration strenuously resisted in court — to remove Tsarnaev from death row, commute his death sentence to life imprisonment, and thereby guarantee that he can never be executed for his crimes.

Tsarnaev is one of 40 murderers in federal prison who have been sentenced to death. In recent days anti-death penalty activists, journalists, lawyers, and religious figures (including Pope Francis) have pressed Biden to empty the federal death row by commuting every existing federal death sentence to life behind bars. The arguments they make are the ones always invoked by death penalty abolitionists: They complain of racial imbalance, they assert that capital punishment has no deterrent effect, they observe that other countries have ended executions, they raise the specter of wrongful convictions, and they claim that death penalty cases are too expensive.

That is the standard case for abolishing capital punishment as a matter of public policy. It is not a case for clemency.

Biden is being urged to issue a mass commutation of the 40 killers on federal death row not as an act of compassion — not because they merit mercy — but as a way to invalidate a federal law that the activists disapprove of. That is not why the Constitution empowers presidents to exercise clemency, and even impassioned death penalty foes should be deeply wary of encouraging this or any president to go down that road. If Biden can nullify every federal death sentence, what is to stop another president, a fervent champion of the Second Amendment, say, from using the pardon power to nullify every federal gun-control law? What would prevent a president who ardently supports open borders from granting unconditional clemency to anyone accused of entering the United States unlawfully?

When the Biden administration asked the Supreme Court to overrule the court of appeals and reinstate Tsarnaev’s death sentence, it stressed that only in so doing could the marathon bomber’s case be brought to “a just conclusion.” The same can be said of the other monsters on the federal death row.

Those monsters include Dylann Roof, the neo-Nazi white supremacist who in 2015 methodically shot nine Black parishioners dead while they were engaged in Bible study at the Emanuel AME Church in Charleston, S.C. They include Robert Bowers, who in 2018 opened fire during Shabbat services at the Tree of Life synagogue in Pittsburgh, sending 11 worshipers to early graves. They include Daniel Troya and Ricardo Sanchez Jr., who in 2006, to settle a drug debt, murdered a young married couple and their two little boys on the side of a Florida highway.

Tsarnaev, Roof, and the other killers weren’t sentenced to death casually. In each case, an impartial jury of 12 had to unanimously conclude that they were guilty of capital murder. The jurors also had to unanimously agree that the appropriate penalty was not life imprisonment but death. Like all capital defendants in federal court, Tsarnaev, Roof, et al., were represented by attorneys with expertise in defending death penalty cases.

Unlike the victims they bombed, shot, or stabbed to death, there was scrupulous due process of law for each of those murderers. And at the end of that process — when all the evidence had been presented, all the arguments made, all the appeals adjudicated — it was decided that, for the terrible crimes they committed, they deserved the worst penalty our legal system allows. Biden is being urged not to secure justice but to thwart it. Don’t do it, Mr. President.