As a society, we have agreed that some crimes are so horrific that they belong in a separate category. These are acts in which the perpetrators victimize not only their immediate target but all of us — which is why we label them “crimes against humanity.”

And that’s why the effort by hard-right politicians in Guatemala to free war criminals from prison is a matter that concerns everyone.

Not many outsiders realize that a genocide unfolded in Guatemala, less than a thousand miles from U.S. shores. The killing took place during the Cold War and after it, from 1960 until 1996, when the parties signed a peace accord and agreed to the National Reconciliation Law.

Like other transitional justice arrangements, that agreement demanded painful sacrifices from a country that had suffered greatly. Guatemalans decided to look unflinchingly at what they had done but, for the sake of peace, to forgive almost all crimes committed in the course of the war. The state would punish anyone found guilty of the worst atrocities, including crimes against humanity, massacres and kidnapping.

Now a group of legislators wants to repeal all exceptions to the amnesty. If they succeed, dozens of perpetrators of crimes against humanity would walk free within 24 hours of a signature by President Jimmy Morales.

Morales is already pushing against the rule of law, trying to shut down a United Nations-backed anti-corruption commission. Lack of accountability contributes to violence, one reason Guatemalans are fleeing to the United States. Approving amnesty would fuel that process.

The amnesty legislation has faltered in the face of domestic and international condemnation, but it has not been fully withdrawn. At any moment the Guatemalan Congress could make a push, and by then it would be too late to stop it.

If Guatemala unravels its reconciliation agreement, it would affect transitional justice efforts around the world, all of them delicate and vulnerable.

In 1999, after two years of investigations, a U.N.-backed Historical Clarification Commission found that more than 200,000 Guatemalans had been killed in the war. The overwhelming majority were civilians. Indigenous Mayans in particular were viewed by government forces and their paramilitary allies as supporting the rebels.

The commission found that “agents of the state committed acts of genocide,” and that 93 percent of the documented violations had been committed by the government and its backers, while 3 percent were carried out by the Marxist rebels.

In one case, the military’s special forces, the Kaibiles, abducted and killed all 200 members of the village of Dos Erres. The soldiers bludgeoned men and boys to death, and raped and strangled women and girls. In another, officers kept 11 Mayan Q’eqchi women as sex slaves in an army camp, repeatedly raping them over six years. Countless places and names evoke civilian massacres; the security forces killed with machetes or machine guns. The commission report noted that “the rape of women, during torture or before being murdered, was a common practice.”

The government perpetrating most of the atrocities was supported by Washington. President Bill Clinton apologized for that in 1999, saying it was wrong to back such a regime. The United States became a champion of transitional justice, playing a key role in finding and prosecuting Kaibil members living in the United States.

Then, in a landmark case, Guatemala indicted the military dictator who led the country during some of the most brutal parts of the war. In a trial that transfixed the nation, the former strongman, Gen. Efraín Ríos Montt, was convicted of genocide and crimes against humanity.

The 2013 conviction was thrown out less than two weeks later on a technicality, but Ríos Montt remains the only head of state ever prosecuted and convicted of genocide in his own country. He died at age 91, five years after his overturned conviction. Since then, efforts to rebuild Guatemala’s judiciary and strengthen rule of law have become mired in dispute.

Conservative allies of the president complain that exceptions to the amnesty law are disproportionately applied to the military. Critics note that almost all of the worst violations were committed by that side.

Government supporters have a majority in Congress, and the amnesty legislation easily passed the first of three required readings. The changes would immediately free dozens of prisoners convicted of grave human rights violations and stop the prosecution of about a dozen more already indicted and awaiting trial. The legislation would also foreclose the possibility of any more prosecutions over mass killings for which far too few have been held to account.

The third reading was canceled on order of the Inter-American Court of Human Rights, which ruled that the legislation violates Guatemala’s international commitments. But the bill could be resurrected on short notice.

The European Union, the United Nations and others have spoken forcefully against it. Washington, meanwhile, has offered bland criticism, declaring itself “concerned” about the law.

The push to exonerate perpetrators of crimes against humanity is an affront against humanity. The U.S. government should make that starkly clear to Guatemala. It is in everyone’s interest that the original law be observed as it was intended. Anything else would worsen impunity in Guatemala, add to the forces propelling its people to leave the country, and send a troubling message to current and future combatants considering reconciliation in other corners of the world.

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