A good rule of thumb for dealing with Iran is to always remember that the Islamic Republic is not a normal nation, guided by the rule of law. When it detains foreign nationals, they are not prisoners awaiting due process. They are hostages to be traded for concessions -- by a regime founded by hostage takers. This really should go without saying. But evidently Britain needs a reminder. Take the latest "scandal" involving a minister in the government of Theresa May, foreign secretary Boris Johnson. Critics of Johnson fault him for new charges being brought by Tehran against Nazanin Zaghari-Ratcliffe, a British and Iranian citizen arrested last year on trumped-up national security charges. Earlier this month in testimony before Parliament, Johnson incorrectly said Zaghari-Ratcliffe had been involved in teaching people journalism. An Iranian judge pounced. He claimed that Johnsons testimony proved she was also guilty of spreading propaganda against the regime, possibly doubling her sentence. Johnsons political opponents in the Labour Party are now blaming him for further endangering Zaghari-Ratcliffe. They are not alone. Richard Ratcliffe, the prisoners husband, told the Times of London, “There is a direct link between Boris Johnson’s comments on Wednesday and Judge Salavati, the harshest judge that you can find hearing her case on Saturday, where she is now facing a double sentence." Sir Paul Jenkins, the former chief of the British governments legal department, tweeted that the gaffe was "extraordinary even by the grotesque standards" of Johnson. He added: "Our nation suffers, individuals suffer because of his slack incompetence." Never mind that Johnson himself clarified his remarks both in Parliament and also to Irans foreign minister, Javad Zarif, that he was not asserting Zaghari-Ratcliffe was in Iran to teach journalism (heaven forbid), but rather expressing the most extreme version of the charges against her. The problem with blaming Johnson for the cruelties of an Iranian judge is that it confers legitimacy to a kangaroo court. The judge in Zaghari-Ratcliffes case, Abolghasem Salavati, has sentenced Iranians to jail for working with the US on an AIDS prevention program. He metes out sentences to political reformers. He is a scourge to journalists, human-rights activists and students. To pretend that he is interested in evidence and procedure is delusion. He is a “judge” in the same sense in which Iran is a “republic.” Don’t let the title fool you. Then there is the recent history of Irans detention and prosecution of dual nationals. The regime uses these prisoners as bargaining chits. Thats what happened with Jason Rezaian, the Washington Post journalist arrested and detained on espionage charges because he had had the temerity to apply for a job at the Obama White House. Eventually the Iranians allowed him to leave the country with a few other Iranian-Americans, but only after the US commuted the sentences of Iranian proliferators. It’s not reasonable to think that a comment by Britain’s foreign secretary affects the standing of the detained citizen. She is a hostage, not a defendant. This is a shakedown, not a trial. And hostage taking has worked for the Iranians. They traded the Americans at the US Embassy it seized in 1979 for the Algiers Accord and a promise of American non-interference. A few years later, the Iranians traded hostages taken by Hezbollah in Lebanon for Israeli anti-tank missiles. Money was paid to the Iranians to release American hikers in 2011. The latest hostage is Zaghari-Ratcliffe, and the UK can’t afford to get distracted blaming anyone other than the guilty parties. Nadhim Zahawi, a member of Parliament from Johnsons Conservative Party, summed this up Thursday. He told me in an interview: "Its worth remembering who the culprits are, the Iranian Revolutionary Guard Corps and the Iranian regime. They are holding an innocent mother of a 3-year-old baby who is a British citizen, who should be home with her anxious husband in England." He added that the Labour Party "needs to be careful not to be used as stooges for the Iranian regime." Zahawi was being charitable. Jeremy Corbyn, the Labour Partys leader, was paid to guest host a call-in show on Irans English-language propaganda network known as PressTV. That network lost its UK broadcasting license in 2012 after it aired a forced confession from a Newsweek journalist. And yet Corbyn appeared again on the network six weeks after its broadcast license was revoked. None of this is to say the UK shouldnt try to bargain with Iran for the return of British citizens. These are hard choices with no easy answers. But that bargain should be made with open eyes. Boris Johnson hasnt provoked Zaghari-Ratcliffes jailors. To assert that he has is to pretend Irans hostage takers are statesmen, that its show trials are free and fair.Bloomberg