Pocahontas Descendant to Sen. Warren: Take DNA Test and I'll 'Welcome You to Our Heritage'

'How Can He Live With Himself?': FL Shooting Victim's Father Suing Broward Deputy

Judge Andrew Napolitano appeared on "Fox & Friends First" Wednesday morning to react to a new report that Special Counsel Robert Mueller told President Trump's legal team that he could subpoena the president to appear before a grand jury if Trump refuses an interview with Mueller's team.

It appears to have been the first time Mueller raised the possibility of compelling Trump to testify as part of his investigation into allegations of collusion between the Trump campaign and Russian officials ahead of the 2016 election.

Napolitano noted that a lengthy list of questions Special Counsel Robert Mueller wants to ask Trump was leaked this week. 

"If he goes before the special counsel, he's not under oath and it's voluntary. If he goes before a grand jury, he is under oath, and it's not voluntary. He has to go," Napolitano explained.

He said Trump wouldn't have to answer questions if he invoked his Fifth Amendment right, although Trump famously said only mobsters invoke the Fifth Amendment.

He pointed out that Trump has repeatedly said that he's eager to speak to Mueller because there was no collusion between his campaign and Russia and no obstruction of justice, and he has absolutely nothing to hide.

"Legally, it would protect him, but politically it would be catastrophic for this president who said he can't wait to tell his story to plead the Fifth," Napolitano said.

Bongino Blasts Mueller Probe: 'You Investigate a Crime,' Not a Person

Judge Nap: Leaked Questions for Trump Are 'Treasure Trove' Into Mueller's Thinking

ICE Director Homan Delayed Retirement Because Trump Asked Him to Stay