I cannot answer your question, as I'm only familiar with US law, but let me point out that you live in the land of DMT-containing acacias. You can harvest all of the extractable plant material you might need, assuming you have any access to nature whatsoever.
As I said, I don't know Aussie law, but I do know governments, and even if customs let a suspicious package slip through, it could still put you on a list. If it got confiscated, I'm sure you'd be on a list. Even if it takes some effort, in the long run finding an acacia grove you can harvest from would be the better choice.
That is, unless you were wanting to make purple-pink dye with it. Then you're in trouble.
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