Depends on what kind of firearm the magazine is for, and its capacity. You need to satisfy Canadian firearms law - which in general restricts handgun magazine capacity to 10 rounds or less. There may also be restrictions based on the firearm the magazine will work in (ie. does it fit and function in any restricted weapons, which include just about any handgun with a barrel shorter then 4").
Since firearm owners must be licensed in Canada, and the firearms themselves registered, I don't know how that affects a recipient of a magazine in Canada.