Drug trafficking in Australia is deemed a very serious offence, one for which legislators and courts have ruled general deterrence is paramount and 'little mercy' should be shown (Clune  VR 567, O'Bryan and Marks JJ, 576). A principal challenge has been how to effectively differentiate and sanction participants in the drug trade particularly how to differentiate 'traffickers' from those who consume or purchase illicit drugs for personal use alone (people whom legislators and courts have determined ought be sanctioned more leniently; MCCOC 1998b). To assist in this endeavour, all Australian states and territories have adopted legal thresholds that specify quantities of drugs over which offenders are either presumed to have possessed the drugs 'for the purposes of supply' and liable to sanction as 'drug traffickers' (up to 15 years imprisonment in most states), or in the case of Queensland, liable to sanctions equivalent to drug traffickers (up to 25 years imprisonment). Yet, in spite of known risks from adopting such thresholds, particularly of an unjustified conviction of a user as a trafficker, the capacity of Australian legal thresholds to deliver proportional sanctioning has been subject to limited research to date. This paper summarises key findings from a Criminology Research Grant funded project. The broader project examined this issue in two different ways whether the thresholds are designed to filter traffickers from users and whether they enable appropriate sanctioning of traffickers of different controlled drugs. Herein, the focus is on the former to what extent Australian legal thresholds unwittingly place users at risk of unjustified and disproportionate charge or sanction as traffickers.