Measures proposed for planetary defence: Obstacles in existing international law and implications for space arms control

Whereas the Earth is showered by extraterrestrial matters on a constant basis, most of them cannot survive the very high heat produced in their entry into the atmosphere to make a terrestrial impact. Impacts that are capable of inflicting terrestrial casualties and damages are even rarer. However, their consequences can be high, and even so nowadays with the change of human settlement patterns on the Earth. With the development of space science and technology, human beings are now capable of predicting possible impacts with some accuracy, and even minimizing the chance of actual collision. For the later purpose, many proposals have been put forward, which either employ weapons readily found on the Earth, or envisage newly developed technologies that could nevertheless be used for military purposes. This short note applies existent international law to these measures, and attempts to shed some light on their implications for ongoing discussions of space arms control.