MARY LOUISE KELLY, HOST:
As the impeachment inquiry has unfolded, President Trump has repeatedly raised the notion of treason. Here he is today at the White House speaking about Adam Schiff.
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PRESIDENT DONALD TRUMP: Frankly, they should look at him for treason because he is making up the words of the president of the United States - not only words, but the meaning. And it's a disgrace. It should not be allowed to happen.
MICHEL MARTIN, HOST:
It's not the first time Trump has suggested someone investigating him has committed treason. Here he is in May responding to a reporter, naming several former FBI officials.
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UNIDENTIFIED REPORTER: Who specifically are you accusing of treason?
TRUMP: Well, I think a number of people. And I think what you look is that they have unsuccessfully tried to take down the wrong person. If you look at Comey, if you look at McCabe, if you look at probably people - people higher than that, if you look at Strzok, if you look at his lover, Lisa Page - his wonderful lover.
KELLY: Now, treason is one of only three crimes defined outright in the text of the U.S. Constitution.
ROBERT LITT: Treason against the United States shall consist only in levying war against them or in adhering to their enemies, giving them aid and comfort.
MARTIN: That's Robert Litt. He was general counsel for the office of the director of national intelligence in the Obama administration. The bottom line, he says, is that it has to involve rebellion or outside enemies. For that reason, there haven't been any treason prosecutions since the years around World War II.
LITT: There were some American citizens who adhered to the Nazis and spied within the United States and were convicted of treason. But, for example, the Rosenbergs, who stole the atomic bomb secrets and gave them to the Russians, were not tried with treason. They were tried for espionage because there was no enemy with whom we were at war at the time.
KELLY: Even if the president were to order an investigation, Litt says it's not likely to go very far.
LITT: The attorney general and the Justice Department are still going to be bound by the statutory definitions. And I would not think that the Department of Justice would spend very much time investigating a member of Congress for treason because he makes statements that the president doesn't like.
KELLY: That is Robert Litt, former general counsel in the office of the director of national intelligence.
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