The disciplines of international law and geopolitics have evolved around the same object – the exercise of State power in space. But the interaction between geopolitical and legal categories has not been properly examined yet. Similar to international law, geopolitics focuses on certain, albeit not formally binding, laws that govern or explain the conduct of States in relation to space. There is room for the geopolitical laws reasoning to lead to outcomes that differ from those required under international legal obligations of States. In other cases, geopolitical laws and reasoning could actually explain why certain international legal rules and institutions are what they are. This contribution is the first attempt to study geopolitics and international law in parallel to each other. It is demonstrated that the evolution of geopolitical thinking, whether as part of a particular expansionist or containment agenda or as scientific approach, has constantly reflected on the categories of international law, and also has been used in practice by States to justify their particular conduct in defiance of international legal requirements. At the same time, international law has traditionally left to States the room for pursuing their geopolitical agenda without breaking the requirements of international law. It is here that the significance of geopolitical factors for international law becomes clear, as the allegedly lawful expansionist action by States can lead, and has repeatedly led, to reactions that involve breaches, and potentially damage the integrity, of international law. Despite geopolitical agenda being allegedly lawful, it still has to observe certain geopolitical laws in order to avoid broader negative repercussions both for that agenda and for international law.