From my understanding of this news release, this is only a Canada Post thing. It just sounds like they've had a few bad experiences in the past where they evacuated postal offices because they found fake grenades and artillery shells. I'm not sure how they "found" them in the past, since I was under the impression they didn't scan or x-ray packages within Canada, but maybe 9/11 changed things and now they do. They don't say what happens if you are caught sending this stuff, like a fine or something more serious.. they don't really give anymore details.
Like I said before, it's just a heads up. If your paranoid and plan on sending this sort of stuff, like those fake grenades or those 40mm cartridges for the M203, simply use a different courier.
Reuters Canada had a funnier headline:
Stop mailing fake grenades, Canadians told