Flynn, an outspoken Trump backer during the presidential campaign, was named national security adviser shortly after the election. Prior to the inauguration, Flynn was reported to have spoken with Sergei Kislyak, Russia’s ambassador to the United States, about sanctions placed on Moscow over election interference. Such a conversation would have been a huge break from protocol—and, according to some analysts, a violation of a federal law against civilians conducting foreign policy, though no one has ever been prosecuted for the offense.

Flynn denied having discussed sanctions with Kislyak, both to reporters and to Vice President-elect Mike Pence, who repeated that denial in a January 15 CBS News interview. On January 26, Yates informed White House Counsel Don McGahn that intercepted communications indicated Flynn was being untruthful about the conversations. The administration took no public action. Nearly three weeks later, after news about Yates’s bulletin to McGahn leaked to the press, Flynn was forced to resign.

It’s easy enough to see why Trump is upset about the leak. Every president is infuriated by damaging leaks, and Trump seems to have been fine keeping Flynn on the job despite having lied to Pence—the problem was that the public knew.

Since Flynn stepped down, he has encountered more trouble. He was revealed to have lobbied for the Turkish government from summer until November 2016, but failed to register as a foreign lobbyist until March. The chairman and ranking member of the House Oversight Committee recently said they believe he broke the law by receiving payments from the Russian and Turkish governments—both because he did not seek requisite permission ahead of time, and because he did not disclose them after the fact. Flynn, who in 2016 said, “When you are given immunity, that means you probably committed a crime,” has reportedly sought immunity from the bodies investigating Russian interference.

Trump’s argument—setting aside his boilerplate bluster about fake news—is that it’s actually Barack Obama who is to blame for the whole fracas. Flynn was head of the Defense Intelligence Agency under Obama, until he was forced out in 2014. In 2015, Flynn traveled to Moscow for a celebration of the Kremlin-backed network RT, where he was reportedly paid $45,000 and ate dinner with Vladimir Putin. He received renewed security clearances in 2010 and in 2016, both under the Obama administration.

Because of this, Trump argues that it was actually Obama who fell down on the job. There are a couple problems with this. One is that Flynn was informed ahead of time that he was obligated to seek permission before receiving the money from either Russia or Turkey. A second is that he was obligated to disclose both of those after the fact. Flynn’s obligations aside, the January 2016 background check should probably have turned up the Russian trip, which was publicly known. (It’s worth noting that background checks are conducted by career staff, not political appointees.)