The aim of the article is to present the issue of peaceful use of outer space in terms of public international law and selected domestic acts. The research problems include: the scope of validity of treaties fundamental to international space law, the evolution of the development of space law in the context of not only acts of treaty law, but also selected acts of domestic law, as well as the issue of the principle of freedom of space exploration in relation to the demilitarization of space both in both passive and active aspects. The authors of this article put forward a research hypothesis according to which the applicable sources of space law allow for a slow and systematic erosion of the principle of peaceful use of outer space, which is additionally forced by the actual actions of individual states. When preparing this article, the authors relied primarily on the analysis of legal acts - in Polish, Russian and English, and additionally on the literature on the subject, in order to then be able to verify and possibly improve the research hypothesis. On this basis, it was concluded that modern space law is only theoretically based on five fundamental treaties as sources of public international law. In practice, the parties to the Agreement regulating the activities of states on the Moon and other celestial bodies of December 18, 1979 are not, and never have been, neither the two states that started the race for space exploration, nor the states that subsequently broke the monopoly in space of these two entities and are currently investing significantly in space technology. This seems quite alarming, because the provisions of the Moon Agreement confirmed, developed and specified many provisions of the space treaty, including provisions regarding the absolutely peaceful use of outer space. The only positive aspect of the treaty’s approach to the use of outer space remains the Treaty on the Prohibition of Tests of Nuclear Weapons in the Atmosphere, in Outer Space and Under Water, signed in Moscow on August 5, 1963. This act met with considerable understanding among the international community, as evidenced by the adoption of obligations under this act by many countries.