What is the Logan Act, and why does it matter?

Vice President Pence (left) shakes hands with former national security adviser Michael Flynn before the start of a joint press conference between President Trump and Japanese Prime Minister Shinzo Abe on Friday. Flynn resigned Monday night after multiple reports were published noting he had misled the vice president and others in the administration.
Vice President Pence (left) shakes hands with former national security adviser Michael Flynn before the start of a joint press conference between President Trump and Japanese Prime Minister Shinzo Abe on Friday. Flynn resigned Monday night after multiple reports were published noting he had misled the vice president and others in the administration.