On August 19, 2009, the Republic of Korea launched Naro Rocket (or KSLV-1: Korea Space Launch Vehicle-1) which was developed by Korean technology, but unfortunately failed to settle in the earth orbit. Regarding the technology for launching and developing the first Korean satellite KITSAT-1, it is possible to say there have been considerable advances on space technologies in Korea. Nowadays, Korea is managing several satellites in the earth orbit, and doing its own best to be one of outer-space developing countries in the international community. In this context, the time is coming to analyze international space law and practice relating to managing satellites in the earth orbit in full detail among law scholars and experts in Korea. Concerning militarization issues in outer space, it became one of the controversial issues in international space law field since the U.S. government declared the Strategic Defense Initiative in 1983, so-called Excalibur project, which mainly aimed to develope anti-ICBM system in low earth orbit. Recently, Bush administration also declared National Space Policy(NSP), which regarded operating space objects in outer space and developing outer space as its own national interest. The NSP contained military use of outer space to protect the U.S. national interest and security. Furthermore, the fact that North Korea recently launched the satellite named Kwang Myung Sung 2 and the news about the plan to develop ICBM by North Korea within 10 years surely show that the militarization of outer space issue is not theoretical or imaginary one anymore. In this regard, among scholars and experts in Korea it is necessary to look into the various legal issues of militarization in outer space, particularly in low earth orbit. This article mainly dealt with the current legal regime established under “the 1967 Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies” (hereinafter referred to as “the Outer Space Treaty”) from the standpoint of public international law. Through analysis on such a legal regime and the interpretation of the relevant provisions in various international treaties and documents, this article gave the answers to the following three questions. (i) What is the attitude of the Outer Space Treaty on militarization of outer space, in particular toward a problem of developing and deploying the conventional weapons? (ii) Whether a State could develop and deploy the conventional weapons in the earth orbit for the purpose of exercising the right of self-defense under international law or not? And finally (iii) Whether the relevant provisions of the UN Charter might be the legal ground to deploy conventional weapons in the earth orbit or not?