In Oz, refuellers are very touchy about topping up used drums - quality control forbids it. But if the drums are in good condition (no dents, no rust, bungs in good nick) and you know the fuel man well, he might do a deal for you. But he might be liable if there is any contaminant in the drum. if he cannot satisfy the quality requirements and seal the drum, he is leaving himself open to lawsuits.
However, if you own some drums and have your own bowser, there is little anyone can do to stop you filling your own drums, as long as you do the normal tests for water and other junk.
