Reuters ON the afternoon of May 14, moments after authorities pulled Dominique Strauss-Kahn off an Air France flight on suspicion that he had tried to rape a hotel maid, the former International Monetary Fund chief pulled rank. “I have diplomatic immunity,” he told police, and asked to speak with the French consulate, according to court papers. Hours later, as police questioned him about his diplomatic status, and whether he was claiming immunity, Strauss-Kahn did an about-face. “No, no, no. I am not trying to use that,” he said. “I just want to know if I need a lawyer.” More than four months on, with the criminal case now behind him, Strauss-Kahn is taking another crack at invoking diplomatic immunity -- this time to fend off a civil suit filed by Nafissatou Diallo, the maid who accused him of sexually assaulting her in his suite at the Sofitel Hotel in Manhattan. In court papers filed on Monday, Strauss-Kahn's lawyers asked a judge to dismiss the civil suit, arguing that as head of the IMF, Strauss-Kahn was entitled to absolute diplomatic immunity, even after he had resigned. But international law experts and criminal-defense lawyers said convincing a judge to buy the immunity argument will be a formidable task. “I think (his lawyers) are feeling somewhat emboldened and they are trying anything. But I don't think it has legs,” said Bradley Simon, a prominent New York criminal-defense lawyer. Simon said if the immunity defense had any legitimacy, Strauss-Kahn's lawyers would have raised it early in the criminal case, before he stepped down as head of the IMF. Strauss-Kahn resigned on May 18, saying in a letter to colleagues that he wanted “to protect” the institution. Strauss-Kahn's lawyer, William Taylor, who also represented him in the criminal case, wrote in an e-mail that his client “chose not to raise immunity in the criminal case in order to defend against the false charges and to clear his name.” “We have said from the beginning that this matter was an attempt by plaintiff and her lawyers to extort money from Mr. Strauss-Kahn,” Taylor wrote. Prosecutors dropped all charges against Strauss-Kahn on Aug. 23, weeks after acknowledging that they had grave doubts about Diallo's credibility. In arguing that the court should dismiss Diallo's civil suit, Strauss-Kahn's lawyers cited a 1947 United Nations convention under which heads of specialized agencies are immune from civil and criminal suits, regardless of whether they were acting in their official capacity when the alleged harm took place. The United States is not a party to the convention but Strauss-Kahn's lawyers insisted that its absolute-immunity provision has “achieved the status of what is known as ‘customary international law'” and that it must be honored. Kurt Taylor Gaubatz, an associate professor in the Graduate Program in International Studies at Old Dominion University, called this argument a stretch. The convention is a “relatively obscure treaty that hasn't been tested,” Gaubatz said, adding that he was not aware of any other accusations of criminal acts by agency directors. “Customary law develops through practice. And there is no practice here.” __