The capture of an alleged Islamist terrorist recruiter in Milan four years ago in an operation carried out by U.S. and Italian intelligence could have been a model for transatlantic cooperation in counterterrorism. Instead, it is becoming Exhibit A in how European politicians are working against the U.S., undermining the fight against Islamic terrorism and endangering the NATO alliance.

An Italian court last month ago indicted 25 CIA agents and a U.S. Air Force lieutenant-colonel on charges that they kidnapped Osama Mustafa Hassan Nasr and illegally took him back to his native Egypt, where he was imprisoned and, he claims, tortured. Five Italians were also charged - including the top two officials at the military intelligence agency at the time.

Nasr, a radical imam also known as Abu Omar, is a terrorist suspect who had been under Italian police surveillance since 9/11. In the covert operation that took place in February 2003, Italians and Americans worked together to apprehend Nasr, before whisking him back to Egypt against his will and without the permission of an Italian court. The Milan prosecutor, Armando Spataro, contends that Nasr was "kidnapped." Such "extraordinary rendition," he tells us by phone, is illegal under Italian law, and he's ensuring that the "rules are really followed... without any political considerations."

As in many such operations, the particulars are in dispute. But no one, including the Italian prosecutors, doubts that Nasr posed a security risk. In 2005, a Milan court, at Mr. Spataro's behest, issued an arrest warrant for Nasr, charging him with building a terrorist network in Europe that actively recruited terrorists, including for Iraq. Eight of his accomplices have been sentenced to up to 10 years in prison on similar charges, and Italian authorities believe more are at large.

Why Nasr was captured rather than arrested in 2003 isn't clear. According to a July 2005 story in the New York Times, which cited unnamed current and former American officials, the CIA was concerned that Nasr was plotting to attack the U.S. Embassy in Rome. For whatever reason, the U.S. wanted him off the streets while the Italians weren't ready to arrest him. The CIA won't comment. The government of Silvio Berlusconi - who was Prime Minister at the time - denied any foreknowledge of the rendition.

No one seriously claims, however, that the CIA agents were in Italy without the explicit knowledge and participation of Italy's security services. This is the crucial point - and explains why the indictments are a hostile act against the U.S. By long-established international legal practice, the official agents of one country operating in another with that state's permission are immune from prosecution. The status of forces agreement that governs U.S. troops stationed in Italy enshrines this principle at least for official conduct.

If the CIA agents did anything wrong, that's up to American authorities to decide. Mr. Spataro, an independent prosecutor, can indict as many Italians as he wants. His pursuit of U.S. government personnel, however, makes him a rogue. Aggravating the harm, Mr. Spataro cited the 25 agents by name, possibly putting their lives in danger. The trial in June, presumably in absentia, would likely do further damage by exposing intelligence-gathering techniques. Call it a tutorial for al Qaeda on how to avoid detection.

The appropriate response by Prime Minister Romano Prodi would have been a swift announcement that he would reject any extradition request from the court. Instead, Mr. Prodi merely hinted that he might do so before his government collapsed on Wednesday night. Having won the confidence vote last week to resume power, he has a second chance to finally fulfill his obligation to his U.S. treaty allies and reject extradition.

European politicians are more at fault here than any prosecutor. Since the 9/11 attacks in the U.S., many European leaders have been playing a double game, working with the U.S. to root out terrorist plots on the sly - and saving countless lives - while publicly condemning "American methods" in rhetoric that has fed rising anti-Americanism. It doesn't help that many Europeans embrace the preposterous legal notion of "universal jurisdiction," the idea that an ambitious prosecutor can indict and try anyone for an alleged crime committed anywhere in the world.

This is the climate in which, for example, a German court this month issued arrest warrants for 13 CIA agents allegedly involved in transferring a German-Lebanese terrorist suspect, Khaled al-Masri, to Afghanistan for questioning. It made no difference that Mr. al-Masri had been arrested in Macedonia. Also in Germany, prosecutors are considering whether to bring war-crimes charges against former Defense Secretary Donald Rumsfeld, Attorney General Alberto Gonzales, former CIA Director George Tenet and other senior civilian and military officials. Mr. Rumsfeld, Colin Powell and Dick Cheney were targeted by Belgian courts until the law there was changed. And so on.

European officials need to understand the risks they're running if they keep this up. Italy and the U.S. are NATO partners, but such an alliance is meaningless if "allies" make a habit of prosecuting each other for cooperating against a common threat. Italy's political grandstanding is endangering NATO, as well as the lives of millions on both sides of the Atlantic.