The concept of long-term sustainability of outer space activities is based on rational assumptions regarding outer space as a limited resource, which will inevitably shrink in the long term if States do not take appropriate preventive measures. The arguments for this are all the stronger as it concerns a real threat to the safety of space operations, and what is more, to their continuation in the future. The legal status of outer space determines the responsibility of States for the activities of both governmental and non-governmental entities. The UN COPUOS Guidelines for the Long-term Sustainability of Outer Space Activities strongly remind of this. This is an important element of this document, which should be considered not only in the context of liability for damage caused as a result of space activities, but also in the context of liability for violating the principles adopted in the key treaty of international space law, which is the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies of 27 January 1967. The main purpose of this article is to present the assumptions of the concept and, in their light, to refer to its structural treaty connotations in the field of generally recognized international responsibility of the State for space activities. The study is also intended to show workable solutions adopted in national law that implement the COPUOS Guidelines, as a necessary and inevitable direction of national activity of countries wanting to explore and use outer space safely and responsibly.