Fox News senior judicial analyst Andrew Napolitano has argued that Donald Trump did obstruct justice, with “unlawful, defenseless and condemnable” behavior related to the investigation of Russian interference in the 2016 election.

In the opinion column Did President Trump obstruct justice?, the host of the Liberty File on Fox Nation argued that the Mueller report illustrates clear and intentional obstruction of justice, constituting legal grounds for impeachment.

Napolitano, a former superior court judge in New Jersey, thereby contradicted the attorney general, William Barr, who decided there was insufficient evidence to establish that the president had committed obstruction of justice.

Napolitano’s column was accompanied by a video, shot outside Fox News HQ in New York, which spread rapidly on social media. Trump is an avid viewer of the network and user of Twitter. He did not immediately respond.

An FBI investigation into contacts between Trump aides and Russia began before Robert Mueller was appointed special counsel. Mueller’s investigation expanded to include instances of possible obstruction, among them the firing of FBI director James Comey, who told investigators he believed Trump fired him after he refused to call off an investigation into the former national security adviser Michael Flynn.

In his Fox News column, Napolitano argued that with the release this month of the redacted version of Mueller’s report, we “now know why Trump was so anxious for the FBI to leave Flynn alone”.

Flynn pleaded guilty to lying to the FBI about discussing sanctions with the then Russian ambassador, Sergey Kislyak, a communication Napolitano said “could have been unlawful if it interfered with American foreign policy”.

Trump fired Flynn but, Napolitano wrote, “in his plea negotiations with Mueller, Flynn revealed why he discussed sanctions with Kislyak – because the pre-presidential Trump asked him to do so.

“An honest revelation by Trump could have negated Flynn’s prosecution. But the revelation never came.”

Napolitano said Trump’s attempt to steer the FBI away from Flynn, successful or not, constituted obstruction, which he defined as attempts “to impede or interfere with any government proceeding for a corrupt or self-serving purpose”.

Napolitano disagreed with the special counsel’s decision not to make a determination on obstruction of justice.

“Mueller laid out at least a half-dozen crimes of obstruction committed by Trump,” he wrote, “from asking former deputy national security adviser KT McFarland to write an untruthful letter about the reason for Flynn’s chat with Kislyak, to asking [former campaign aide] Corey Lewandowski and then White House counsel Don McGahn to fire Mueller and McGahn to lie about it, to firing Comey to impede the FBI’s investigations, to dangling a pardon in front of Michael Cohen to stay silent, to ordering his aides to hide and delete records.”

“The essence of obstruction,” he wrote, “is deception or diversion – to prevent the government from finding the truth.”

Napolitano also claimed Mueller knew Barr would block any indictment of Trump along obstruction grounds because the attorney general “has a personal view of obstruction at odds with the statute itself”.

Barr’s view, according to Napolitano, is that obstruction can only occur if someone is impeding an investigation into a crime they committed.

“Thus, in this narrow view, because Trump did not commit the crime of conspiracy with the Russians, it was legally impossible for Trump to have obstructed the FBI investigation of that crime,” Napolitano wrote.

He concluded that though such a position is at odds with broad law enforcement opinion and “wrong”, it provides Congress the opportunity to use Mueller’s report as grounds for impeachment, which would be a question of political viability, not evidence.