Republic of Korea has a special type of organization, so-called ‘public institutions’, which is neither central nor local government agency, but also no private company. Public institutions are established and operated for special purposes of the state. In principle, public institutions’ workers should be guaranteed 3 labor rights, since they are employees. However, public institutions involved with national defense, such as the Korea Institute for Defense Analyses, Defense Agency for Technology and Quality, Agency for Defense Development, and Military Outplacement Training Institute deny their employees’ 3 labor rights. The denial of the 3 labor rights by these institutions is related to national security and public welfare under the Constitution. The denial of the 3 labor rights of private workers is based on Article 37 (2) of the Constitution. In these cases, whether the underlying Acts is unconstitutional must be reviewed through the excessive prohibition principle. Judging only from the Acts that deny the 3 labor rights, the legislative purpose is justified. However, the suitability of the means, the minimum of infringement, and the balance of legal interests are not recognized. Those Acts that deny the 3 labor rights should be reasonably amended. Otherwise, the legal status of those employees should be changed to civil servants.