Peter Howard told Federal Court court on Friday that Black's case is so "unique" that the advisory council currently reviewing his membership could give Black the hearing without having to make the exception again for a long time.
"Halley's comet is due back in 2061 and this situation is unlikely to arrive again before its return," Howard said.
"There won't be another Conrad Black who fights for 10 years in the face of this kind of pressure because there hasn't been to date," he said, referring to Black's legal battles in the U.S., where he was convicted of fraud and obstruction of justice.
In response, Justice Yves de Montigny questioned whether forcing the order to grant Black an oral hearing — complete with witnesses — would set a precedent for other members placed under review.
Black, 67, is asking Federal Court to force the hearing on the council as it decides whether to recommend the Governor General revoke his prestigious 1990 appointment as an officer of the Order of Canada.
The council notified him last July they were considering termination of his membership, but Black's letter the next month asking to appear before them was met with a "10-month delay" before they denied his request, Howard said.
If expelled, Black would be the fifth person to lose membership in the order, the privileges of which are "purely symbolic," federal lawyers argue.
Black did not attend court but argues in an affidavit that he should be able to look the 11-member advisory council "in the eyes" as they consider his status.
Chaired by Supreme Court Chief Justice Beverley McLachlin, the council may recommend to the Governor General that an appointment be rescinded when a member has been convicted of a criminal offence, or if their conduct strays significantly from recognized standards of public behaviour.
Howard told court that Black has a right to speak his views aloud and take questions from the council since his credibility is on the line in light of his U.S. convictions.
"He's going to tell them to their face that 'I didn't do anything wrong and here's why not,'" the lawyer said.
Whether the order's rules on just how a member is allowed to personally make their views before the advisory council are open to judicial intervention was a point returned to repeatedly in the federal court room.
Government lawyer Christine Mohr said whether the council reads or hears submissions is up for the order to decide, arguing the process falls under the Governor General's "royal prerogative" and is thus beyond the reach of a judicial review.
And, she told court, the rules are clear to see.
"There's no promise of anything other than a written representation," she said. "There's no circumstances that justify an exemption of that rule."
Mohr denied claims by Black's legal team that a call by council to kick Black out would automatically lead to his expulsion.
She said the Governor General has "unfettered discretion" in making such decisions.
When asked by Justice Montigny whether losing his status would ding Black's public standing — a point Black's legal team says warrants a fully voiced council appearance — Mohr said that any harm to Black's reputation would instead be a consequence of his convictions.
Justice Montigny reserved his ruling Friday and did not immediately set a decision date.
Black, who renounced his Canadian citizenship in 2001 to become a member of the British House of Lords, recently returned to Canada on a temporary resident permit following his May release from a Florida prison.
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