Final answer:
The rule of occupation is a legal doctrine that allows a state to claim sovereignty over a territory if it exercises effective and continuous authority over it and the territory is not already under another state's sovereignty.
Step-by-step explanation:
The rule of occupation is a principle in international law which holds that territory can become the possession of a state if it is not already under the sovereignty of another state and if this state is effectively and continuously maintaining its authority over that territory. The practice is associated with historical contexts where territories were acquired through colonization or military conquest. For instance, during this process, a state may establish a sphere of influence where it exerts political or exclusive control in various ways, such as establishing military bases or monopolizing areas of business. Establishing sovereignty can also involve the administration of territory, potentially changing its legal framework, which can include the systems of taxation and the regulation of inhabitants' property, such as houses, gardens, mills, fields, vineyards, etc.