Judge Andrew Napolitano broke down the legal issues at play following the explosive allegation by President Donald Trump that President Barack Obama ordered a wiretap of Trump Tower during the presidential campaign.

Napolitano said much of the analysis in the last few days is "mixing apples and oranges," emphasizing that the FBI can obtain search warrants to look for evidence of crimes, while the NSA can obtain a warrant to investigate national security matters.

The Fox News senior judicial analyst said the NSA is allowed by law to capture "all digital information" within the United States and the president can obtain transcribed copies of those intercepted communications.

He added that the FISA statute states "the President of the United States can order surveillance on any person in the United States in conjunction with a certification filed by the attorney general."

"It's profoundly unconstitutional but it is legal because the statute says it," said Napolitano. "Think about this: if you're Barack Obama and you have the ability by making a phone call to hear what Donald Trump is saying, would you bother getting a warrant? Why would you get a warrant?"

Obama's spokesman said Saturday that no such order was ever given.

"A cardinal rule of the Obama Administration was that no White House official ever interfered with any independent investigation led by the Department of Justice. As part of that practice, neither President Obama nor any White House official ever ordered surveillance on any U.S. citizen. Any suggestion otherwise is simply false," the statement read.

Shannon Bream asked whether Trump could access a surveillance order from the previous administration if it exists. 

"I don't know that FISA would give him the orders, but he could get them from NSA," the judge explained.

Watch the judge's full analysis on "America's Newsroom."

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