I may be wrong, but I think the biggest problem with listing aboriginal artifacts on eBay is the chance of exporting prohibited or restricted items. If you hope to export them, you need to have the artifacts examined and certified by an Expert Examiner from the National Cultural Heritage Committee; Class A aboriginal artifacts can never be exported, Class B artifacts require a permit for export, anything less than 20 years old requires no pernits at all.

Buying and selling such artifacts within Australia is perfectly legal, so all you really need to do is to make sure you aren't leaving an option for overseas bidders to buy it.