Satellite mega-constellations are becoming very popular. Nevertheless, their deployment entails the potential to negatively impact the pristine view of the night sky and - by extension - to hamper ground-based astronomical observations. This paper evaluates the applicability of existing legal instruments towards achieving greater protection of space sciences vis-a-vis commercial space activities. Firstly, it examines whether the term “space activities” can be interpreted so as to include ground-based astronomy, in an effort to understand how different needs and the freedoms of exploration and use of Outer Space (OS) can be best balanced. Furthermore, the paper reviews the application of environmental law principles and discusses the obligation of States to conduct EIAs in order to minimize light pollution and protect the Dark and Quiet Skies under the “due regard” principle of Article IX OST. Finally, this paper discusses pragmatic proposals towards the preservation of the space environment and the sustainability of space activities.