Photo: The Canadian Press

The Canadian government is in a tribunal hearing today, arguing against the imposition of duties on Bombardier planes.

The country's ambassador to Washington says potential duties of up to 300 per cent are illegitimate for several reasons.

First, David MacNaughton says the case that Bombardier C-Series imports will cause material injury to rival Boeing is based on speculation and conjecture — prohibited under U.S. and world trade law.

He also tells the U.S. International Trade Commission there's no evidence Bombardier planes will be exported to the U.S.; that the C-Series does not compete with Boeing aircraft; that Boeing has a seven-year backlog in sales, invalidating its plea of an injury; and that duties will hurt U.S. jobs, as Bombardier accounts for 23,000 jobs in nine American states.

Outside the hearing room, MacNaughton says the case has broader implications.

He says anti-trade rhetoric in the U.S., not just from the Trump administration, has emboldened companies to launch commercial attacks on their foreign rivals.

The British ambassador to the U.S. made a similar argument at the hearing.

Boeing argues that government subsidies have allowed their Canadian rival to infringe on potential markets; that C-Series sales are already hurting orders; and that the recent Bombardier-Airbus partnership to build in Alabama is a ruse that would disappear if duties go away.