President Donald Trump had a constitutional right to tell FBI Director James Comey not to prosecute former national security adviser Michael Flynn, constitutional expert Alan Dershowitz said Saturday.

In remarks on "CNN Newsroom With Ana Cabrera," the Harvard law professor said there are two remedies for those who are outraged over Trump's firing of Comey after the president reportedly pressed Comey to drop his investigation of Flynn – "amend the Constitution, [or] don't vote for him."

"But don't try to expand the existing criminal law in violation of civil liberties to do what Stalin did, where [secret police chief Lavrentiy] Beria said, 'Show me the man, I'll give you the crime,'" Dershowitz said. "That's not America."

Dershowitz said impeachment is a political solution.

"The problem with impeachment is exactly what Candidate Trump did during the campaign – and you can't impeach a president who ran and won based on all the things he's done, all the things he's now doing," he said.

"There's not that much new that would warrant either an impeachment, certainly not a criminal prosecution."

Dershowitz, who confesses he voted for Hillary Clinton, said "I care deeply about not expanding criminal statutes to fit people we don't like."