An admitted al-Qaida member who served as an aide to Osama bin Laden, transcribed martyrs’ wills for two 9/11 hijackers and operated a radio so the terrorist ringleader could listen to news about the attack feels he got a raw deal when he was convicted of conspiracy to commit war crimes by a military commission and insists the U.S. Constitution requires trial by a civilian jury for that crime.

Ali Hamza Ahmad Suliman al Bahlul's attorney Michel Paradis urged a 10-judge en banc appeals panel in the nation’s capital Tuesday to look past the unsympathetic Guantanamo Bay detainee, warning the executive branch would be able to present any crime to military commissions, even those historically tried by the judicial branch, if Bahlul's conviction is upheld.

“This was a test case from the very beginning,” Paradis said, repeatedly referring to the commissions set up to prosecute al-Qaida terrorists as “special executive trial chambers” that were not allowed for use beyond prosecution of internationally recognized war crimes.

So far, Bahlul has fared well fighting a set of three 2008 convictions. Last year he shed convictions for providing material support to a terrorist organization and solicitation of others to commit war crimes, on ex post facto grounds, leaving only the inchoate conspiracy to commit war crimes conviction, which a three-judge panel earlier this year ruled also should be tossed.

The case presents a complex thicket of legal issues and the Supreme Court may have the final word.

Paradis’ appeal for the judges to stand up for their branch of government against encroachment from elected branches received a mixed response from the jurists, half of whom already have ruled one way or the other.

In June, Judges David Tatel and Judith Rogers found in Bahlul's favor and Judge Janice Rogers Brown -- who was silent Tuesday -- dissented. Judge Karen Henderson last July broadly disagreed with his pleadings and Judge Brett Kavanaugh wrote he believed “conspiracy, unlike material support for terrorism and solicitation, has long been an offense triable by military commission.”

Kavanaugh, sounding open-minded despite his earlier opinion, told Paradis on Tuesday that "under the plain language of Article III [of the Constitution] you have a great case." The judge focused instead on the outer limit of what crimes could be considered by military commissions.

But Justice Department attorney Ian Heath Gershengorn declined to say what limits, if any, should apply to crimes triable by military commissions, saying the prerequisites for using that trial format are the suspect being an enemy belligerent during a period of hostilities. Judges “should be wary” of establishing the outer limits, he argued, and should show deference to the executive branch.

“We need to know what the consequences of our decision will be,” pressed Tatel, asking Gershengorn if visa-holders apprehended in a U.S. city with explosives and a mass transportation system’s map could be tried by military commission.

“That may well be enough,” the government attorney said, to qualify the suspects for a military commission, the benefits of which, he explained during the hearing, include loosening hearsay and Miranda rules that are difficult to apply to battlefields.

Rogers, expressing unease about the government’s rubric for using a military commission, noted the meaning of the term enemy combatant can change over time.

Judge Nina Pillard, an active participant in the hearing, said she felt the government was forcing the matter, at one point raising her voice and telling Gershengorn she was “just baffled” and “really puzzled about why we are here," as she felt Bahlul could have faced other charges that clearly are permitted in a military commission.

Gershengorn said other charges, such as for aiding and abetting and participating in a joint criminal enterprise, could have be brought against Bahlul, though he’s not sure if the government could win or if retrial would even be possible, given the U.S. prohibition on double jeopardy.

If Bahlul does prevail against the conspiracy conviction and life sentence, he's probably not going to be let free. The rosiest scenario for him likely is transfer from solitary confinement to general population at the U.S. detention facility in Cuba. He could possibly be retried on other charges.

Paradis said he believes the government’s argument essentially amounts to his client being a bad person and therefore worthy of trial by military commission. But the precedent set by the court, he warned the judges, could open the door to any “ordinary vanilla conspiracy” or other crime being sent to a commission.