The potential for development of a new ‘space mining’ industry has been rather topical lately with private companies increasingly interested in the perspective of utilizing in situ resources of celestial bodies. In the absence of a clear international legal framework, the effort to provide legal standards for the industry has been supported at the national level, notably by Luxembourg in 2017 and the United States of America in 2015 which adopted legislations recognizing the appropriability of space resources. This triggered intense debates about space resources utilization, which has been the subject of several high level intergovernmental conferences, workshops and discussions in the past year. For the most, current efforts and legal research focus on the acceptability within current international law standards of the appropriation of such resources and on deciding which, between national legislations and the adoption of an international agreement, should be the most suitable. However, these questions have already been addressed in similar situations on Earth, with the legal framework for the appropriation of marine and deep seabed resources. These rich conversations still miss the crucial issue of the protection of outer space’s environment. Industrial exploitation of resources is bound to impact outer space’s environment, potentially causing environmental damage as it did on Earth. Therefore, the issue of space resources’ sustainable management needs to be legally regulated. The aim of this thesis will therefore be to analyze the legal issues pertaining to the question of appropriation in the scarcely explored context of sustainable development in outer space. Thus, the main research question of the proposed PhD thesis will be: how does the current legal framework regulate potential space mining activities while the too often forgotten necessity to address the protection of outer space’s environment has yet to be defined?