The process of liberalization of international trade and of Foreign Direct Investment (FDI) has constituted a broadly accepted trend during the last few decades and FDI inflows have expanded constantly since the end of the 1980's. However, signs of a certain crisis of the positive and one-way attitude towards international trade and FDI exist nowadays. The financial crisis, the change in the origin of the FDI derived from the new geo-strategic reality arising out of the crisis, the growing participation of foreign sovereign actors in international trade and investment, the changing environment for national security or the quest to protect technologies and sectors of the economy considered vital for the host country, its sovereignty and competitiveness have led many countries to set forth mechanisms to evaluate FDI proposals before they are implemented. Korea is not alien to this trend. As a matter of principle the protection of national security is a legitimate goal of any state. However, there is a risk of these kinds of instruments being politicised, and the potential negative consequences of a broad interpretation of the notion of national security remain. The creation of these screening systems has taken place in an atmosphere of liberalisation of investment, and their introduction has ultimately constituted a sort of exception to it. But this atmosphere is changing negatively very quickly and the peril to use these screening systems as an excuse to impose hidden limitations on free trade and investment increases. The Republic of Korea, as many other countries in the world, is not vaccinated against this danger.