Concern Trolling -

...So what law did Flynn violate? According to the New York Times, he may have violated the Logan Act, an antiquated statute that prohibits private citizens from negotiating with foreign adversaries. The Times reported that Obama administration advisers believed Flynn may have negotiated a deal with Russia just after Obama had imposed new sanctions and expelled Russian spies as punishment for Moscow's interference in the election. On Thursday, the Washington Post reported that he may have misled FBI agents investigating the phone calls.  

There are a few important points here. To start, there is no indication that Flynn made any quid pro quo with the Russians. The Times reports this, and I have confirmed it with my own sources. Second, the Logan Act, which dates back to 1799, is likely unconstitutional. The Justice Department does not prosecute Americans violating it. And in this case, the private citizen was about to become the national security adviser. If it's illegal for incoming U.S. officials to discuss policy with foreign adversaries, then the hard work of preparing the transition of a foreign policy agenda for an incoming administration will be outlawed. The FBI investigation is more serious, but so is disclosing the bureau's ongoing investigations to the press. 

It's also been reported that Flynn had contacts with Russians during the election. That's a bit more troubling, but in and of itself it means very little. It's also not unprecedented. In 2008, an Obama foreign policy adviser, Daniel Kurtzer, traveled to Damascus to offer the government there his views on the Syria-Israeli peace talks.  

Many Democrats, including former Secretary of State John Kerry, took meetings with Iran's ambassador to the United Nations during George W. Bush's final years as president, at a moment when our military leaders accused Iran of killing U.S. soldiers in Iraq by providing militias with improvised explosive devices. If Bush's FBI had launched Logan Act investigations in that period, would Democrats have cheered on the leaks of the investigations?...

...According to the Washington Post, acting attorney general Sally Yates felt compelled to take this information to the White House at the end of January because she was so concerned that Flynn was compromised.

This sounds like concern-trolling to me. If Flynn forgot the brief discussion of sanctions in his phone call with the Russian ambassador, as he claimed in his resignation letter, it's far-fetched to think the Russians could coerce him to betray his country to not expose the "lie." This is why it's so important to release the transcripts of these phone calls to the public, as former U.S. attorney Andy McCarthy ...

https://www.bloomberg.com/view/articles/2017-02-17/separating-fact-from-innuendo-in-the-flynn-fiasco