As commercial space activity increases, the practice of patented inventions in outer space has become a live legal problem. This poses a novel challenge to the territoriality principle of patent law, which has traditionally operated on the premise of practice within national territories. While the stages at which devices such as satellites and payloads are produced, transferred, exported, or imported domestically can be addressed under existing frameworks, post-launch operations in orbit present a gap. Specifically, there is no express standard for determining whether the use of an object or the performance of a process in orbit constitutes practice within the Republic of Korea. Furthermore, while the Outer Space Treaty confers jurisdiction and control over a space object on the state of registry, its text does not explicitly deem acts carried out in or on board to be practice within the state’s territory. Therefore, the existence of jurisdiction under international law does not, by itself, determine the place of practice under patent law; bridging this gap requires an explicit, separate statutory provision. Against this backdrop, this article categorizes and analyzes the unique issues raised by the practice of inventions on space objects, and examines the formal and structural legislative approaches of major spacefaring nations addressing this problem to chart a path for reforming Korean patent law. Ultimately, such legislative reform should not aim to abolish the territoriality principle or artificially extend the territory of the Republic of Korea into outer space. Instead, it should use the state of registry as a connecting factor to supplement the specific situations in which the locational elements presupposed by territoriality become indeterminate in or on a space object.