Yes they most certainly are, and no there isn't...unless you wanna purchase them from less reputable characters.
http://www.customs.gov.au/site/page.cfm
Yes our customs service is one of the most thorough and well supported Govt departments bar one (Australian Tax office), not a lot gets by customs. If you try and import one of these from anywhere hylian you run the risk of a huge fine and/or imprisonment, and the risk of getting caught is
extremely high. An unknown mate of a mate, tried to import a taser and some sort of BB pistol from the 'States', it was intercepted by customs and they laid a trap for him at the airport, as soon as he arrived he was nicked big time. As of now he is still paying off the fine in installments, if he defaults...no guessing where he goes

Further, all major Australian ports and airports now have specialised imaging hardware for scanning containers, baggage, trucks etc at such a speed that it is no longer picking one at random, they can scan the lot in less time than they used to take!!!
Nice P90 anyway lads, I bet you're having heaps of fun with it