A controversial rationale the Trudeau Liberals are using to justify approving exports of combat vehicles to Saudi Arabia – that these machines could help Riyadh prosecute a war in neighbouring Yemen – is figuring prominently in a Federal Court challenge aimed at stopping the shipments.

Eric David, a renowned human rights legal scholar from Belgium who has acted in major international cases, is lending support to a March 21 lawsuit led by University of Montreal professor Daniel Turp that seeks to block exports of the weaponized armoured vehicles from Canada.

In an affidavit being added to the lawsuit, Prof. David of the Free University in Brussels says he believes Canada is violating international law by shipping arms to a country already accused of massive human-rights violations in Yemen. A United Nations panel investigating the Saudi-led bombing campaign in Yemen found "widespread and systematic" attacks on civilian targets in violation of international humanitarian law.

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Allowing the "sale of armoured vehicles to Saudi Arabia … would violate the obligation to respect and ensure the respect of human rights and international humanitarian law," Prof. David wrote in a 196-page filing.

"The sale of armoured vehicles … becomes an "internationally wrongful act."

As The Globe and Mail first reported, Foreign Affairs Minister Stéphane Dion last week quietly approved export permits covering more than 70 per cent of the $15-billion transaction with Saudi Arabia – a decision that represents the most vital step in determining whether a weapons shipment to a foreign country can proceed or whether it's "illegal," as Ottawa calls it.

The revelation that Mr. Dion greenlighted the bulk of this deal runs contrary to the Liberal claim that the Trudeau government's hands were tied on the Saudi deal.

Many observers had assumed the Conservatives had granted export permits when they signed the deal.

The Liberal signature on the export permits means the Trudeau government has taken full ownership of a decision to sell arms to a country notorious for human-rights abuses.

In the memorandum justifying the export permits, the department of Global Affairs reasons that the light armoured vehicles will help Riyadh in its efforts at "countering instability in Yemen," where the Saudis are fighting Houthi rebels aligned with Iran, as well as combatting Islamic State threats.

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"The acquisition of state-of-the-art armoured vehicles will assist Saudi Arabia in these goals," the memo approved and signed by Mr. Dion said.

When it comes to Yemen, the Canadian government is choosing its words carefully, noting that so far the Saudis have not been found to be using Canadian-made combat vehicles previously sold to Riyadh to commit rights violations there.

Asked about the Saudis' conduct in Yemen on Thursday, Mr. Dion said they're not the only ones that need be held to account. "There are serious concerns that should be raised about all of the parties" fighting in Yemen, Mr. Dion told the Commons foreign affairs committee Thursday, widening the matter to include the conduct of Houthi rebels.

"As far as Yemen is concerned, our priority is to have a peaceful solution found."

Separately, Thursday, Mr. Dion offered only mild support for an NDP proposal by MP Hélène Laverdière to create a Commons committee that would scrutinize arms exports. "I think it's an interesting proposal. I am not sure it's the priority right now – but the committee can certainly decide," the minister told the foreign affairs committee.

Saudi Arabia is regularly ranked among the "worst of the worst" on human rights by Freedom House.