Deactivated Thompson SMG

I saw on Part II of the Canadian Pickers in the UK that they bought a deactivated Thompson SMG with a 20 round magazine from a collector for resale in Canada. I was under the impression that it was not possible to import deactivated weapons from the UK. As well, I also thought that unpinned 20 round Thompson magazines were illegal to own in Canada. Am I mistaken?

No, you're not mistaken. Unless one of them has a firearms license to possess prohibited firearms they wouldn't be able to bring it into the country themselves so they would need to send it to a dealer in Canada with the proper license and then the gun needs to be inspected to verify that it is deactivated to Canadian standards. Basically, it is treated the same as a live machine gun until proven otherwise. Not impossible to import but rather difficult and risky (sometimes the firearms are confiscated or stuck in legal limbo) from what I understand. The magazine only needs to be pinned or otherwise modified to accept no more than 5 rounds to be legal here. That they could accomplish on their own if they know that it needs to be done. As long as it's the legal limit before it gets to the border they are okay.

Considering neither one appears to know squat about military weapons, I would be surprised if they knew anything about the regulations as there was no mention made during the program.

That's the same impression that I had when watching the program.

I hate to read too much into these generic 'history' programs as they are just entertainment for the masses disguised as history; but I do recall on one of the Canadian Pickers adventures into the Yukon that they specifically made mention to how they have to be mindful of the laws with respect to either the sale or export of certain animal parts or archaeological examples - I cannot remember the exact details. I would have thought that in this case some mention would have been made concerning exporting deactivated weapons and unaltered weapons magazines into Canada.

There should certainly be production staff who should be mindful of the laws regarding any collectables. Not just weapons and ammunition. There are some problems with ivory (as carved by POW's) and shipping between countries.