This link should take you to the relevant regulation. I'm having trouble scrolling it on my iPad so try viewing it on a pc

http://www.comlaw.gov.au/Details/F20...#_Toc337213590

Some others here would know the specifics better than I do (and they vary state to state) but as I understand it, if you can establish that you are a collector and that the item you are/were trying to import is a part of said collection, then for imitation firearms (the specific category that G1 Megs falls under) you can obtain from your state's police chief permission to import said item. You could also get more info here:

http://www.ag.gov.au/CrimeAndCorrupt...nfirearms.aspx

I'm not sure if you can get permission retrospectively, but you may be able to. Good luck!