Apologies if this is not applicable as I have not read the whole thread but this is exactly what happened to me and the initial batch of Type 97s imported by Lever Arms in Vancouver.
They wanted to confiscate without compensation. I took it as far as having a date for a court hearing before a judge to see if a case court case was justifiable. Before this happened I was informed that they would fully compensate owners. Long story short I did have to give it up but did receive the full purchase price back from the government.
You may be able to use this argument as precedent setting particularly as it was their mistake in the first place.
At the time there were only 60 rifles and the goverment was conservative. They approved the refunds because they were looking out for firearms owners. I don't think the liberal goverment will be so inclined. Not to mention these rifles are much more expensive 2-3k and there were 250+ imported. So easily 1 million$ or more for compensation.
https://www.cbc.ca/news/politics/rcmp-gun-confiscations-prompt-legal-fight-1.958226