‘Preventive Justice’ was coined by Blackstone, in the late eighteenth century, to describe an area of law devoted to preventing future crime by intervening where there exists ‘a probable suspicion, that some crime is intended or likely to happen’. 1 Governments have long employed ‘preventive justice’ measures that restrain an individual’s liberty on the basis of an estimation of future harm, rather than past acts (even if past acts form part of the prediction of future harm). In England, preventive measures have been traced to the twelfth century, with the power granted to Justices of the Peace to bind over subjects to keep the peace. 2 This preventive jurisdiction was well established by the time Australian colonies enacted ‘Bushranger’ legislation in the 1830s, which permitted the apprehension and detention without charge of a person suspected of being a felon until the suspected felon established, to the reasonable satisfaction of a Justice of the Peace, that he or she was not a felon. 3