The Atlantic first reported on Monday that Trump Jr. received a private message from the WikiLeaks Twitter account on September 20, 2016 — a message shown in tweets produced by Trump Jr.
Napolitano said it is "no crime" for the president's oldest son to have simply been communicating with WikiLeaks.
"This is America. You can talk to anyone about anything," he explained, noting that it would be a legal problem if there was an agreement between Trump Jr. and WikiLeaks.
"If an agreement comes out of the conversation and you're running a federal campaign and the agreement is to receive something of value from a foreign entity, then you have a problem," said Napolitano.
The judge said he believes some of WikiLeaks' releases have been beneficial for Americans to see, but the organization is, nevertheless, an adversary of the U.S. government.
He noted that earlier this year, CIA Director Mike Pompeo denounced WikiLeaks for operating like a "hostile intelligence service" after allegations that Julian Assange's organization acted as a cut-out for Russian intelligence.
U.S. intelligence agencies concluded that emails from the DNC and Hillary Clinton's campaign chair John Podesta were hacked by Russia before being released by WikiLeaks.
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