What is a legal amount of fuel and what is a safe amount of fuel for any circumstance are two different things. A company will stipulate the LEGAL MINIMUM to be carried by their SOP's approved by CASA.CAR 234(the law of the land) stipulates the PIC must carry a SAFE amount of fuel. This is where pilots discretionary fuel comes into the equation. Many factors determine this amount, but it should not be determined by bean-counters or flt.ops departments because, at the end of the day, the PIC has the legal responsibility and will wear the consequences. It is he who will have to prove he carried a SAFE fuel load.