It does says things in the MGP rules that contradict ACU rules, for instance, in the 2006 ACU Handbook it says "leaded petrol mixtures up to 100 octane RON wiil be allowed", in MGP rules it says you can use Avgas. Avgas is approxiamately 102 octane MON/115+ octane RON so according to 2006 ACU rules, everyone on Avgas is running illegal fuel, but theyre not because it says in the MGP regs that its allowed, and the MGP regs have had to be approved by the ACU in the first place. As the witch says, supplementary regs are just that , an addition to what it says in the ACU Handbook.