Our comprehension of the legal means and methods by which military forces are employed, controlled and — where considered necessary — immunised, is incomplete. Some questions are — in a jurisprudential sense — well settled, or at least evolving along a logical, comprehensible, and generally linear course. Thus the scope of the defence power under the Australian Constitution has, on the whole, been relatively consistently interpreted over time as an elastic power — expanding in time of large-scale conflict, contracting in time of profound peace, variably waxing and waning between these two poles in situations of uncertainty less than war but short of settled peace. There have certainly been some new developments in understanding the scope of the power — such as the High Court of Australia’s decision in Thomas v Mowbray (relating to the constitutional validity of the federal control order regime). In this case the majority held that components of the defence power are also exercisable through non-military organs such as the police. But on the whole, our understanding of the power has developed along conceptually and chronologically coherent and logical lines. Similarly, there is no question in the Australian context that this evolution has also been more generally coherent in terms of its interaction with related constitutional questions. Thus Thomas v Mowbray is, in many ways, a belated cross-referral allowing police and intelligence agencies to access authority under the defence power. This merely reflects and accompanies the long established principle that the military forces can likewise be used for law enforcement purposes — as confirmed in Li Chia Hsing v Rankin. It is perhaps justified to say that were we to apply a jus ad bellum / jus in bello approach (law of armed conflict based and thus formally inapplicable, but nevertheless useful) to the problem, the jus ad bellum issues — the when and why of use of military forces in law enforcement operations — are relatively settled, or at least evolving coherently and consistently with their history and precedent.