WATCH: CNN legal analyst doesn’t understand the first amendment

Trump claimed in his brief, which was 14 pages, that the impeachment proceeding is unconstitutional as Trump is no longer President and has returned to private life. He also argued that his speech given prior to the riot at Capitol Hill was covered by the first amendment, and that he could not be held accountable for his supporters storming Capitol Hill afterwards.

"Ya, those are wrong, and they're well-countered by the very long brief the House filed earlier today," said Jen Rodgers, a lecturer at Columbia University's law school. "I mean, you don't have a first amendment right to lie, you don't have a first amendment right to put people in danger, and he did both of those things."

It is unclear what Rodgers was referring to when she said that Trump was lying, but lying is, in fact, mostly covered by the first amendment. Exceptions are made under some circumstances such as perjury, false statements to the government, and defamation, but lying is otherwise protected under the first amendment.

Trump's insistence that impeachment of a former President is unconstitutional, however, may be legally dubious. A post-Civil War era Secretary of War, William Worth Belknap, was impeached, but not convicted, after exiting office in 1876.

The Senate hearing on Trump's impeachment is set to begin on Feb 9.