The U.K.'s Conservative Party-led government is losing its head in a rush to appease the anti-European right.

Home Secretary Theresa May told Parliament today that she had signed a legal-assistance agreement with Jordan, in hopes of clearing the way for the deportation of the radical Islamist cleric Abu Qatada.

No problem with that. Qatada -- Spanish prosecutors once described him as the spiritual leader of al-Qaeda in Europe -- has tied successive British governments in knots. He has been in and out of jail since 2001 when, while living on welfare, he was found with £170,000 in cash, including one envelope marked for Chechnya.

The problem comes with what May said next. If the new agreement doesn't succeed in persuading the U.K. courts that Qatada can get a fair trial in Jordan, she said, then the U.K. will consider withdrawing from the 1950 European Convention on Human Rights, which the U.K. helped to draft. That would also mean resigning from the jurisdiction of the European Court of Human Rights, which the U.K. helped to found.

That would be an extraordinarily irresponsible act. The court, which has nothing to do with the European Union, was formed as part of the effort to spread the rule of law across Europe after World War II. The court is attached to the Council of Europe, an organization of 47 nations including Russia, Turkey and Ukraine. In all, 800 million people have the right to appeal to the court if they cannot get justice at home.

Nothing would please the governments in Moscow, Ankara or Kiev more than for the U.K., one of the historic homes of the rule of law, to declare the European Convention on Human Rights and its court so defective that it has to leave -- even temporarily, just long enough to deport Qatada.

Then they could leave, too. Then they, too, could suspend their membership when a particularly irritating case arises.

Last year, 1,734 Britons took their cases to the European Court of Human Rights. In the same period so did 10,755 Russians, 9,098 Turks, 7,796 Ukrainians, 4,077 Poles and 3,253 Italians. To undermine this recourse for justice in Europe would be a terrible mistake.

Qatada has been convicted twice in absentia by Jordanian courts on terrorism charges. The U.K. gave him asylum in 1993, based on his claim that he was tortured in Jordan. But U.K. prosecutors don't have a case to bring against him for a crime committed in the U.K. Two U.K. courts have ruled against Qatada's bid to avoid deportation, but another U.K. court ruled for him, as has as the human-rights court. (Here is a discussion of the legal complexities of the case.)

The central fact here is that membership in the European Court of Human Rights by definition involves a loss of sovereignty; that's the whole the idea, and why the court is so important. That's also why the court so exasperates British Conservatives.

Thus they are meddling in the justice system in a way that would be all too familiar to Russians. May, who hasn't bothered to hide her ambitions to replace Prime Minister David Cameron one day, is coming at him from the anti-Europe right. Cameron has shifted to please the right on other issues, such as immigration, and this week he echoed May's warnings over the human-rights court.

None of this will win the Conservatives the elections -- only economic competence (or luck) will do that. In the meantime, Cameron and May risk ruining the rule of law in the U.K. and Europe.

(Marc Champion is a member of Bloomberg View's editorial board. Follow him on Twitter.)