Former Trump adviser Steve Bannon was unable to present a "factual" defense of his dismissal of a House January 6 Committee subpoena, but retains a legal defense based on presidential executive privilege for any appeal, former New York federal prosecutor Andrew McCarthy told Fox News on Friday.

McCarthy said the key to Bannon's case, however, may be that legal challenge he purportedly plans to mount, in which the ex-Breitbart executive claimed President Trump shielded him with executive privilege – a defense the Trump-appointed judge in the case disallowed presentation to the jury.

"This is one of those rare cases where the defendant really didn't have any factual evidentiary defense, but he's got a legal defense," he said, adding Judge Carl Nichols found the defense invalid because Bannon had been out of the White House for a while and was no longer on-staff under Trump.

Bannon, a former Breitbart executive who hosts the "War Room" program, became the first person since ex-FBI Agent G. Gordon Liddy to be prosecuted for contempt of Congress.

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Steve Bannon addresses the media

Former Trump adviser Steve Bannon and his legal team (Reuters/Michael A. McCoy)

Liddy, who went on to have a successful career as a conservative radio host and author after President Carter commuted his other Watergate sentences, had refused to be sworn in during an appearance before a House Armed Services Subcommittee.

A transcript of that hearing recounted Liddy addressing Chairman Lucien Nedzi, D-Mich. "With all due respect to you personally and to the body of the Congress, for reasons that will be explained by my counsel I respectfully decline to take the oath as a witness."

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Steve Bannon leaving court

Steve Bannon, former Trump political strategist, departs federal court. (Mark Kauzlarich/Bloomberg via Getty)

While Bannon was convicted by a jury, a Lyndon Johnson-appointed judge decided Liddy's case and sentenced him to six months suspended plus probation. Bannon faces a similar misdemeanor prospect of between 30 and 364 days in prison.

McCarthy later noted that a Republican-controlled Congress at the time pursued similar contempt charges against Attorney General Eric Holder, but remarked it was a foreseeable losing battle to get the Obama Justice Department to prosecute its own boss.

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G. Gordon Liddy

G. Gordon Liddy speaks about Watergate on Fox News Sunday. (Freddie Lee/FOX News via Getty Images)

Holder had refused to surrender documents relating to the Fast and Furious gun-running scandal that reportedly led to the death of Border Patrol Agent Brian Terry.

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"This is a statute… that the Justice Department virtually never enforces," McCarthy added, commenting Democrats are risking a pendulum swing against them in this regard if Republicans retake Congress and seek their own charges and investigations against their political adversaries.