By Alison Frankel

NEW YORK (Reuters) - The December 12 arrest of Devyani Khobragade, a deputy consul general at India's consulate in Manhattan, has precipitated quite a diplomatic brouhaha.

Khobragade, who is accused of underpaying her nanny and falsifying documents to get the nanny into the United States, was handcuffed by diplomatic security staff, turned over to U.S. Marshals and strip-searched before being released on $250,000 bail. As anger escalated in India on Tuesday, with reports that Khobragade was forced to undergo a cavity search, Indian authorities retaliated by removing protective concrete barriers in front of the U.S. embassy in New Delhi. (The Marshals Service has said there was no cavity search.)

On Wednesday, Secretary of State John Kerry expressed "regret" and "concern" to his Indian counterpart, and the White House told reporters that it is looking into Khobragade's arrest "to ensure that all standard procedures were followed and that every opportunity for courtesy was extended."

It's a big mess, but there could be a relatively easy way out for both Khobragade and the State Department: retroactive diplomatic immunity. It's a rare but not unprecedented State Department device to grant foreign officials full immunity for their actions even if they weren't entitled to such broad protection when they committed the supposed misconduct.

VIENNA CONVENTIONS

As a consular official, Khobragade has only limited immunity, unlike high-level embassy personnel and their families. Diplomats and consulate officials are actually covered by two different international treaties, the Vienna Convention on Diplomatic Relations of 1961 and the Vienna Convention on Consular Relations of 1963. And as the State Department explained in its guide for law enforcement on diplomatic and consular immunity, consulate personnel are protected just for actions connected to their official duties. If Khobragade had been an Indian diplomat, she could not have been arrested for mistreating household staff, but a deputy consul is not immune from those charges because they're not related to consulate work.

After the arrest, India appointed Khobragade to its permanent United Nations mission, according to her lawyer, Daniel Arshack of Arshack, Hajek & Lehrman. Arshack told Reuters Wednesday that the transfer to a new post "clothes her in diplomatic immunity, which provides immunity for acts before or after the appointment." In a text message to me, he cited a section of the State Department guide addressing termination of immunity, which says (in part): "Criminal immunity precludes the exercise of jurisdiction by the courts over an individual whether the incident occurred prior to or during the period in which such immunity exists."

That's helpful language for Arshack and Khobragade, but from conversations with a couple of experts and a review of precedent on retroactive diplomatic immunity, I think the issue is more complicated than one sentence in a State Department guide. There are really two questions wrapped up in the Khobragade case: Is she entitled to full diplomatic immunity by dint of her appointment - by India - to a post at the UN? And if she is entitled to broad protection, is the immunity retroactive?

Under the Vienna Conventions and the U.S. law implementing them, the Diplomatic Relations Act of 1978, diplomatic status is conferred on foreign officials by the State Department, not by the countries sponsoring the officials. It is up to the United States, in other words, to decide whether to credential Khobragade as a full diplomat entitled to broad immunity.

THE ABDULAZIZ CASE

By itself, India's designation is not sufficient. There's federal precedent on this point: In 1997, Gambia asserted that a special advisor to one of its missions in the U.S. was immune as a diplomat from criminal bribery charges. Federal prosecutors said he hadn't been designated a diplomat by the State Department. U.S. District Judge Michael Moore ruled that the Gambian official wasn't entitled to full immunity because he wasn't credentialed by the State Department. (The official pleaded guilty and there's no record of an appeal by Gambia.)

A State Department representative indicated in a press briefing Wednesday that it would be up to the U.S. to decide Khobragade's diplomatic status. Deputy spokeswoman Marie Harf said it was premature to discuss any change in the consulate official's immunity because the U.S. government has not been notified of her new appointment. She also said that the State Department would have to sign off. "It is not an automatic thing by any means," she said.

But let's assume that the State Department, which has clearly been rattled by India's rage at Khobragade's treatment, agrees to credential her as a full diplomat. Does her immunity reach back to shield her against actions predating her new appointment? It can, according to Peter Rutledge, associate dean of the University of Georgia School of Law and an expert on international dispute resolution. Retroactive diplomatic immunity, Rutledge said, is quite rare - but it's not unprecedented.

The best-known example dates back to 1982, when Miami-Dade police officers attempted to search the home of Prince Turki Bin Abdulaziz of Saudi Arabia, who was suspected of holding an Egyptian woman against her will. At the time of the raid, in March 1982, Abdulaziz had no diplomatic credentials. He did have a burly security staff, which scuffled with police and fended off execution of the search warrant on the prince's home. Abdulaziz and his family sued Dade County for violating their civil rights. County officials countersued, claiming they were injured in the scuffle with the prince's staff.

KOWTOWING TO ROYALS?

In April 1982, about three weeks after the failed search, the State Department granted Abdulaziz and his family full diplomatic immunity. The prince withdrew his suit against Dade County and moved to dismiss the county's counterclaims, arguing that his diplomatic status shielded him from the suit.

Despite arguments by Dade County that Abdulaziz hadn't been a credentialed diplomat when his guards blocked police from entering his house, the 11th Circuit Court of Appeals upheld dismissal of the counterclaims, holding that the prince had been eligible for diplomatic status at the time of the botched raid, even if he hadn't yet received it. In effect, the ruling endorsed the concept of retroactive immunity.

Skeptics later accused the State Department of kowtowing to the Saudi royal family, but that hardly mattered to Abdulaziz, who faced neither criminal nor civil consequences from allegedly detaining a woman against her will and blocking a police investigation. The Khobragade case has some clear distinctions, especially because the State Department has been involved with her investigation since at least early September, when, according to spokeswoman Harf, U.S. officials first alerted Indian authorities of allegations against their deputy consul general.

It was also diplomatic security officers who arrested Khobragade, not local cops without foreign policy sensitivity. For all we know, the State Department intended to send a message to the international diplomatic corps, which is often accused of cloaking itself in diplomatic immunity to avoid claims of mistreating domestic staff.

On the other hand, retroactive immunity would quell Indian outrage and permit the State Department to save face.

I exchanged texts with Khobragade's lawyer, Arshack, but wasn't able to speak with him.

(Reporting by Alison Frankel; Editing by Ted Botha)

(The opinions expressed here are those of Alison Frankel, a columnist for Reuters.)