Yes and no. It would be very easy for any halfway competent manufacturer to build a pistol the exact shape and size of a Glock with parts that would interchange with a Glock - that's just a question of taking a Glock apart and measuring all the bits and pieces.
The hard part comes when you try to duplicate the quality and performance of the original weapon. And to do that, you more than likely have to duplicate the manufacturing process used to make the original parts. For metal parts, the knowledge needed includes the exact alloy composition of the original, as well as the smelting, forging and tempering process used to harden and toughen the metal correctly. For synthetic parts, it would be the exact mix of polymers (and for things like Glock frames, the type and quantity of metal mixed in with it) and the curing process used to create a part with the desired combination of strength, flex, durability, UV and heat resistance, and so forth .
All of that information will likely be closely held trade secrets of the original manufacturer, who won't be too eager to see it leaked outside the company. After all, if Glock told Colt Canada exactly how it made its polymer frames so that Colt Canada could service CF Glocks, what would prevent Colt Canada from then using that knowledge in later designs of its own?
The thing is, in the firearms world as in many other places, much of this type of information is not patented but instead is just protected by internal company secrecy. The reason: patents eventually expire, and then the information in them is out there and open to anyone to use; company secrets, on the other hand, are .... well ... secret, for as long as the company maintains its security.
That's why the recipe for Coca Cola is still not protected by patent but instead guarded by internal company secrecy after more than a century.
Not if the design owner had licensed Canada to use the design. Otherwise, it would entirely depend on whether or not the copied portions were protected by patent or other intellectual property law.
