Since Russia accused U.S. citizen Paul Whelan of espionage and detained him last week, curious details about the 48-year-old’s personal life have continued to trickle out. He was discharged from the U.S. Marine Corps in 2008 for bad conduct. He has dozens of Russian friends on the Russian social media site Vkontakte.

And he claims citizenship in four countries.

This week, U.S. ambassador to Russia Jon Huntsman visited Whelan in the detention facility in Moscow where he is being held. Whelan, a Michigan resident, was born in Canada, and family ties allowed him also to qualify for British and Irish citizenship. Both European countries are requesting access to him, raising questions about whether Whelan’s many passports could affect potential negotiations for his release.

Michael A. Olivas, a law professor at the University of Houston, told The Washington Post that being a citizen in as many as four countries might be uncommon but that it’s “increasingly common that people would have two or more” passports. “Most people don’t live lives that necessitate, require or even allow four passports,” Olivas said. But “it’s certainly not illegal.”

It doesn’t matter which passport Whelan used to enter Russia. All four countries have the opportunity to assist him. And having ties to so many nations could help him. “What it does is it gives more countries more stake in his situation,” Olivas said.

What remains to be seen is whether one country will speak louder than another on his behalf. Ariel Cohen, a senior fellow at the Atlantic Council think tank, told The Post that “it’s absolutely crucial” for all four countries to work together. Otherwise, he warned, Russia could try to make different arrangements with different countries. “If the group doesn’t speak in one voice, the Russians will manage to get a higher price for him,” Cohen said.

Experts have speculated that Whelan was arrested so that Russia could make a swap with the United States for Maria Butina, the Russian gun rights activist who pleaded guilty to conspiring with a senior Russian official to infiltrate conservative U.S. circles. But Cohen said that Butina will be released soon enough anyway and that Russia might have other bargaining chips in mind.

Whelan’s family said he had traveled to Russia previously and was in Moscow this time for a wedding. BorgWarner, the automotive-parts supplier where Whelan works as corporate security director, has said he was not there on business for the company.

Russia’s domestic security service claims Whelan was conducting a “spy mission.” A guilty verdict could mean 10 to 20 years in prison.

As for the reasoning behind all the passports? A person familiar with Whelan’s case told The Post that he collected them “as a game.”

"There was an ongoing competition with his sister to see who could get the most,” the person said, speaking on the condition of anonymity because of the sensitivity of the case.

Regardless of the reasons for his many passports, they might now come to his aid, Peter Spiro, a law professor at Temple University, told The Post in an email.

“It could be a real practical advantage for him to have the Brits and the Irish piling on,” Spiro said. Both governments “might also serve as a backstop if the U.S. government for whatever reason fails to aggressively pursue his case.”

There is still plenty of mystery surrounding the case. Cohen said he sees “no compelling explanation for . . . his interest in Russia and why he kept traveling there.”

And Spiro warned that “there’s only so much foreign governments can do to rein in rogue action like this, assuming that the detention qualifies as such.”

Amie Ferris-Rotman in Moscow contributed to this report.

Read more:

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Paul Whelan probably isn’t a spy. So why did Russia detain him?

American charged with espionage in Russia has an unlikely background for a spy