Law, College of


Date of this Version



Published in the Proceedings of the 48th Colloquium on the Law of Outer Space (2005): 84-94. IAC-05-E6.2.01. Copyright 2005, Frans von der Dunk. Used by permission.


The discussion on the delimitation, and hence definition of 'outer space' as an area, and subsidiary to that on the need or desirability to have such a delimitation and definition, harks back to the beginning of the space age. Until then, it had been quite clear that every state exercised full sovereignty over the sky above its territory and territorial waters, whilst no one felt the need for finding out how high upward such sovereignty would exactly extend. With Sputnik, for the first time the practical question arose however whether there indeed was an upper limit to airspace, and if so, where it would lie. The debate since then has mainly been a theoretical one, partly because several important space-faring nations did not consider it necessary or even appropriate to establish a legally relevant fixed boundary between 'outer space' and 'airspace' as 'geographical' areas for human activities.

It is the main thrust of this paper, firstly, that this situation is changing. It is contended that in particular the recent adventures of SpaceShipOne which for a brief moment 'dipped' into outer space - if one agrees that outer space begins at an altitude of 100 km - bring the question of where 'outer space' begins back on the table. Consequently, wherever that question is indeed considered relevant, in the absence of any international agreement on such a delimitation or definition, viz. the need or desirability to establish one, other legally relevant means are sought to deal with the issue.

Secondly, such development of alternate means has, in turn, its own indirect impact at the international legal plane. Such various developments as Australian national law referring to a lower boundary for outer space and the need to choose for certification of SpaceShipOne and crew may, in the end, through the mechanism of formation of international custom and opinio juris, lead to a customary legal rule.

The current paper thus, firstly, briefly recapitulates the discussion of the last decades on delimitation and definition of outer space, secondly, refers to a few events which directly touch upon this issue, thirdly, tries to analyse the legal aspects of the solutions chosen to deal with that, including the vexing question of formation of customary law, and finally tries to draw some conclusions with respect to the overarching question: if the sky is the limit, where does it end?