Harvard Law School professor emeritus Alan Dershowitz disagreed with claims that there is an obstruction of justice case building against President Donald Trump, calling it "hope over reality" from some Democrats.
Sen. Dianne Feinstein (D-Calif.) said on "Meet the Press" that a Senate investigation into Russia's meddling in the 2016 presidential election has revealed possible obstruction.
"I see it in the hyper-frenetic attitude of the White House, the comments every day, the continual tweets. And I see it most importantly in what happened with the firing of Director Comey, and it is my belief that that is directly because he did not agree to ‘lift the cloud’ of the Russia investigation. That’s obstruction of justice,” Feinstein said.
On "Fox & Friends," Dershowitz countered that Trump had the constitutional power to fire FBI Director James Comey and to tell the Justice Department who to investigate and who not to investigate.
"If Congress were ever to charge him with obstruction of justice for exercising his constitutional authority under Article II, we'd have a constitutional crisis," Dershowitz said.
He explained that Congress would have to demonstrate "clearly illegal acts" on Trump's part, such as former President Richard Nixon paying "hush money," telling people to lie and destroying evidence in the Watergate scandal.
"There's never been a case in history where a president has been charged with obstruction of justice for merely exercising his constitutional authority. That would cause a constitutional crisis in the United States," Dershowitz said, adding that he hopes Special Counsel Robert Mueller understands that before he considers bringing an indictment or recommending that the matter be referred to Congress.
"And Sen. Feinstein simply doesn't know what she's talking about when she says it's obstruction of justice to do what a president is completely authorized to do under the Constitution."
He added that if Trump truly wanted to impede Mueller's investigation, he could have pardoned Gen. Michael Flynn to prevent him from cooperating.
"The president would have had the complete authority do so and Flynn never would have been indicted, never would have turned as a witness against him," said Dershowitz, a lifelong Democrat.
On "America's Newsroom," Judge Andrew Napolitano came down on the side of Feinstein.
He explained that if Trump asked Comey to end the investigation into Flynn for a non-corrupt purpose - such as if he felt sympathy for his former national security adviser or he wanted the bureau to use its resources on more important matters - it's not obstruction.
However, if Trump did it for a corrupt purpose - such as trying to protect himself or his son-in-law, Jared Kushner, from what Flynn might say - then it is obstruction and there is no presidential immunity, Napolitano said.
"Obstruction of justice is a crime no matter who commits it, if done for a corrupt purpose. It's also an impeachable offense," he said, adding that the charge is "intentionally not easy to prove" for a prosecutor.
On "Outnumbered Overtime," Dershowitz said Mueller charging Flynn with lying to the FBI is actually a show of weakness, not strength.
He explained that if Flynn had strong evidence against Trump, then Trump would have pardoned him, instead of allowing him to make a deal with Mueller.
"The deal is not a particularly good one for the special counsel, because he had him indicted for lying," Dershowitz said. "That makes him a worthless witness."
See more from Dershowitz on "The Ingraham Angle" tonight at 10:00pm ET on Fox News Channel.