Originally Posted by ThunderCactus
-return to sender
I'm guessing are the 3 options
Basically they sent you a letter to tell you why it's being held.
They will have an "expert" decide if this is considered a prohibited item or not.
It it clearly states that it's for airsoft only on the boex ect., they either will let it go or send you an other letter telling you that you have the 3 options above.
If you want to appeal, better find a stupid-proof way to prove your kit fits on a "legal" (read "legal" as "against forum rules, not AV section") airsoft gun. Depending on where you bought it, if the seller has listed a modified TM pistol that is "legal", they you can say it's replacement parts for this model.
You can probably also find a local store that carries the upgraded TMs to write you a letter stating that this is again replacement parts for the "legal" model they have for sale.
You also should include the relevant sections of the Criminal code/Firearm act/CBSA memorandum (can't tell you what here, not AV section).
It's a lot of work/time for a receiver kit...
You might want to check if you can have someone in the US where you can reship/export and import the kit yourself after (drive down and declare properly on the way back, DON'T SMUGGLE! That can fuck you life).
Also, RTS/reship is EXPENSIVE, because at that point it is considered a dangerous good/prohibed item and you need a bonded carrier that can export prohibited firearms (hint, CanadaPost/USPS is NOT).