Michael Flynn resigned this week as President Trump’s national security adviser after it became apparent that he had lied to Vice President Mike Pence and other White House officials about a conversation he had with a Russian diplomat about U.S. sanctions. Since such communication came before Trump was sworn in—and therefore before Flynn was officially on the job—it appeared to violate an obscure, centuries-old statue known as the Logan Act that bars private citizens from interfering in diplomatic matters. What seems to have cost Flynn his job, however, was not the communication itself but the embarrassment his attempted cover-up caused the White House.

It now appears Flynn may have lied to more than the White House about what he discussed with Ambassador Sergey I. Kislyak in a conversation that was captured on a routine wiretap of diplomats’ calls. The Washington Post reports:

Former national security adviser Michael Flynn denied to FBI agents in an interview last month that he had discussed U.S. sanctions against Russia with that country’s ambassador to the United States before President Trump took office, contradicting the contents of intercepted communications collected by intelligence agencies, current and former U.S. officials said.

Flynn never appeared to be in any real jeopardy of being punished under the Logan Act, and congressional Republicans have to date shown no interest in pursuing the matter any further. But lying to the FBI is a felony, and doing that is a bigger deal than violating a little-known statute from 1799. Theoretically, Flynn’s lie to the feds could open him up to criminal charges—which would be more than a touch ironic given Flynn’s penchant for leading “lock her up” chants directed at Hillary Clinton during the campaign.

Still, prosecution seems unlikely. The power to prosecute Flynn ultimately lies with the Justice Department, which is headed by Attorney General Jeff Sessions, who in turn reports to Trump. During his press conference on Thursday—during which he said a number of other crazed, baffling, and outrageous things—the president offered a strong, albeit not logically sound, defense of Flynn. “I don’t think he did anything wrong,” Trump said. “If anything, he did something right.”

Update, Feb. 16, 2017, at 10:50 p.m.: CNN is now reporting that the FBI is unlikely to pursue charges against Flynn, citing investigators who stated that Flynn was “cooperative and provided truthful answers. … [T]hey don’t believe he was intentionally misleading them.”