There have been many people commenting it would have been illegal for Obama to listen to Trump's phone calls from Trump Tower, and to the eventual president's in-person conversations, but that is not true, Napolitano said.
"In my view, it's immoral, and profoundly unconstitutional, and utterly wrong, but it's lawful because Congress has said it is lawful," Napolitano said. "This was power given to every president from Jimmy Carter up to and including Donald Trump."
The power was not intended for presidents to spy on political enemies, Napolitano said, but "the language is so broad, that it would authorize it."
"The last thing in the world the intelligence community wants is an investigation by Congress, which will expose how truly pervasive spying is," Napolitano said. "The intelligence community captures everything we say on our mobile devices. Every time we touch a key on our mobile devices, on our desk tops, every conversation on land line, every piece of data that goes across any fiber in the United States into or out of the United States is captured digitally by the NSA."