Jared Kushner's Russia back channel was unusual. But is it illegal?

Diplomatic back channels like the one President Trump's son-in-law set up with the Russian government are "an appropriate part of diplomacy," the White House said Tuesday as it sought to douse a growing controversy over the Trump team's contacts with the rival power.

But experts say the secret talks Jared Kushner sought with Russia would be different from back channels typically used by U.S. governments in the course of international relations.

For one thing, Kushner held no formal position in the government at the time he first approached Russian officials at Trump Tower last December, before Trump was sworn in. And the discussions were apparently set up to operate without the knowledge of the U.S. government.

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The existence of a secret back channel could raise a number of legal issues. The Logan Act, for example, prohibits citizens from conducting unauthorized diplomacy. There's also the Espionage Act, which prohibits the disclosure of classified information, and the Foreign Agent Registration Act, which prohibits anyone from acting as a secret agent of a foreign power.

Whether the talks were illegal could depend on what Kushner aimed to accomplish in talks with Sergey Gorkov, an associate of Russian President Vladimir Putin and the head of the state-owned Vnesheconombank, a Russian bank subject to sanctions imposed by President Obama. Details of those meetings — which have become the latest focus of a sprawling FBI investigation into Russian interference in the 2016 presidential campaign — were reported last week by the Washington Post and The New York Times.

But press secretary Sean Spicer, addressing the issue in a press briefing for the first time Tuesday, declined to elaborate on the purpose of the Kushner-Gorkov back channel or what the president knew about it.

"I'm not going to get into what the president did or did not discuss," he said. And while Spicer did not deny reports of the existence of a back channel, he said they were "not substantiated by anything but anonymous sources that are so far being leaked out."

Kushner's ties to the Russian government have caught the attention of federal investigators running the FBI investigation into Russia's interference in the 2016 election. One key question: Whether Kushner intended to undermine U.S. foreign policy.

One source close to Kushner told the Associated Press that Kushner had spoken to Russian Ambassador Sergey Kislyak about opening up a line to Moscow about Syrian peace negotiations.

That could violate the Logan Act. But that law, first passed by Congress in during the John Adams administration, has never been successfully enforced.

"Imagine that the back channel was so that Jared could get tips about where to buy the best vodka in the United States. If that's all that happened, it's not espionage. It's just really stupid," said Stephen Vladeck, a University of Texas law professor. "I still think that we're light years away from either a Logan Act or an Espionage Act investigation."

Trump's national security adviser, H.R. McMaster, said last week there are legitimate reasons for quiet diplomacy. "Generally speaking about back channel communications, what that allows you to do is to communicate in a discreet manner," he said.

And indeed, there are often good reasons for government officials to have secret contacts with each other, said Anthony Wanis-St.John, an American University professor and author of Back Channel Negotiation: Secrecy in the Middle East Peace Process. Those back channels allow two sides to negotiate without public posturing and internal opposition, decreasing the risks if talks fall through.

The Kushner back channel is different, he said. "In this case, we're talking about an unofficial representative of the Trump campaign and a banker with ties to the Kremlin," he said. "Neither can bind their governments. There is a tinge of something that is less than transparent, and improper."

Because contacts first occurred during the transition, they exist in a sort of legal gray area: President Obama was still constitutionally in charge of foreign relations, but Trump was in the process of appointing his national security team in preparation to take over the job.

The conversation about Kushner's back channel would likely be different if these discussions were taking place post-election, Wanis-St. John said, as even sitting presidents have set up back channels. Former president Richard Nixon did it with his National Security Adviser, Henry Kissinger, who often left the Secretary of State out of the loop on his contacts with the Russians.

Still, any kind of secret discussion can risks consequences, he said. "Bypassing your official diplomats is tricky business. When you're hiding things from your own bureaucracy, there's the taint of something illegitimate."