Like a dripping corrosive liquid, ISIS and the response it provokes from governments are slowly eating away at key human rights principles. Driven by a desire to appear tough on the extremist group, Western democracies are compromising on principles they have defended for years. Each compromise, on its own, may appear small or limited to exceptional cases, but together, these compromises are eroding the edifice of key protections that have been built over the last half century.

The latest casualty is the United Kingdom’s long-standing opposition to the death penalty and its corollary refusal to extradite or share evidence in cases in which the death penalty could be exercised. The Daily Telegraph has published extracts from a letter from UK Home Secretary Sajid Javid to U.S. Attorney General Jeff Sessions, in which he agrees to hand over intelligence to help prosecute captured ISIS members Alexanda Kotey and El Shafee el-Sheikh, both members of ISIS’ infamous cell of British jihadists knows as the “Beatles.” This in itself is unexceptional. What is exceptional is that Javid says in the letter that the UK will not seek any “assurances” that the pair will not face the death penalty in the U.S.

The British government, like other European governments, has for decades refused to extradite people alleged to have committed serious criminal offenses, including acts of terrorism, to the U.S. and other countries without an assurance that they would not be subject to the death penalty. This policy is based on firm human rights norms, which prohibit transfer of an individual to somewhere that they may risk inhuman treatment (as may happen on death row in the U.S.), and opposition to the death penalty, long abolished in the UK and across most of the European continent.

The British policy also extends to refusing to provide evidence or cooperation in trials where the death penalty is being sought or where there is a risk of torture or ill-treatment. The UK maintained this position even in the immediate aftermath of the Sept. 11, 2001 attacks. Indeed, the UK government has refused to extend legal cooperation to prosecution of detainees in Guantanamo Bay, and instead supports calls for the prison’s closure.

Javid’s letter acknowledges this policy. He notes in his letter that “it is the long-held position of the UK to seek death penalty assurances, and our decision in this case does not reflect a change in our policy on assistance in US death penalty cases generally, nor the UK Government’s stance on the global abolition of the death penalty.” If that’s the case, why did he find that “there are strong reasons for not requiring a death penalty assurance in this specific case”?

Javid provides no details. Is it because he thinks that the U.S. will not pursue the death penalty? The U.S. has not said anything to suggest that and it seems unlikely given these men have been publicly accused of kidnapping, torturing and murdering U.S. and U.K. citizens. Or is it because the U.K. revoked their citizenship, as has been widely reported, but not yet officially confirmed by the U.K. government? Nowhere in the published excerpts does Javid make this argument and in the past, the U.K. has not limited its policy of no collaboration in death penalty cases to British nationals. Nor can simply revoking citizenship with the stroke of a pen absolve the U.K. from its duty to avoid exposing them to the risk of capital punishment or other serious human rights abuse.

The answer may actually lie in another U.K. government document from which the Telegraph also quoted in its report. Issued on the same day as the letter and circulated to key civil servants, a government briefing reportedly notes that Javid and Boris Johnson, then U.K. foreign secretary, decided to share evidence with the U.S. on the two ISIS members “without seeking death penalty assurance” as “they concluded that the risks associated with no prosecution being brought against Kotey and El-Sheikh if UK evidence is not shared, outweigh the risks of direct UK assistance to a conviction that could lead to execution and the implications for the UK’s wider death penalty policy.”

Take the time and reread the sentence. This is not language that defends a longstanding principle of British policy and fundamental human rights norms, but rather the language of competing policy interests and compromises.

Moreover, the second document referenced in the Telegraph’s exposé says that the U.K. government “will not lobby the US not to send them to” Guantanamo despite its preference for federal trials and a desire to see that prison closed. And so, it appears that standards on fair trial, due process and adherence to the rule of law – all undermined at the Guantanamo Bay detention camp – are also up for compromise. But they don’t have to be.

The prosecution of these two men, like other ISIS members suspected of committing heinous crimes, is important and is something that Human Rights Watch has long called for. But why shouldn’t the U.K. insist on the same guarantees from the U.S. that it has sought in cases of other suspected terrorists? Why compromise on a key principle when it is possible to articulate support for U.S. prosecutions in federal courts while insisting on the same assurances usually sought from the U.S. that the death penalty will not be applied?

The U.K.’s position is particularly troubling given that the parents of the U.S. hostages, which these men are accused of torturing and killing, have opposed the death penalty for them. In a powerful joint op-ed in February, the parents of four American ISIS victims wrote that they “agree with the longstanding British government position that it would be a mistake to send killers like these to the military prison at Guantánamo Bay, or to seek the death penalty in court. Either path would make them martyrs in the eyes of their fanatic, misled comrades in arms — the worst outcome.”

British officials may try to present its position in these cases as a compromise of necessity to get the U.S. to prosecute these men. But U.S. authorities are perfectly capable of prosecuting people alleged to have committed terrorism offenses without recourse to the death penalty.

The leaked letter is a stain on the moral authority of the U.K. government as it seeks to promote human rights around the world. It represents a massive step backward in building and promoting a criminal justice system in which the death penalty has no place. And it can be viewed as a victory for countries like China, Saudi Arabia and Iran, which have been fervent proponents of the death penalty.

AP Photo/Hussein Malla: A Kurdish security officer, right, escorts Alexanda Kotey, left, and El Shafee el-Sheikh, center, allegedly among four British jihadis who made up a brutal Islamic State cell dubbed “The Beatles,” at a security center in Kobani, Syria, Friday, March 30, 2018.