Recently in Korea it is passionately disputed regarding criminal investigation system whether Article 139 of Korean Criminal Code is constitutional or not. Article 139 of Korean Criminal Code says as follows : Article 139(Obstruction of Official Duties for Vindication of Human Rights) A person who, performing police duties or assisting in such duties, interferes with the execution of duties of a public prosecutor concerning the vindication of human rights or who does not follow his instructions concerning the vindication of human rights, shall be punished by imprisonment for not more than five years or suspension of qualifications for not more than ten years. Korean Constitutional Court ruled the provisions of the latter part of the preceding article is not against the Constitution. One of judges, Justice Gonghyun Lee, argued that this clause is unconstitutional on the grounds of “void for vagueness." In this review firstly is examined how this article was legislated in 1953 and what problem and criticism has been raised. Then is reviewed whether the provisions of the latter part of the preceding article is unconstitutional on the grounds of “void for vagueness." The Article 12, paragraph (1) of the Korean Constitution prohibited punishing “unless it is so authorized by an Act or without due process of law." This clause requires that criminal statutes should be drafted in a clear and understandable fashion. In this review it is concluded that the provisions of the latter part of Article 139 fails to meet this clarity standard and is unconstitutional on the grounds of “void for vagueness." Lastly, is discussed whether the provisions of the latter part of Article 139 is unconstitutional on the grounds of “void for unnecessary." The Article 37, paragraph (1) of the Korean Constitution required criminal statutes to restrict freedoms and rights of citizens ‘only when necessary.' A punishment should not be more severe than is necessary when punishing someone for a crime. In this review it is concluded that the provisions of the latter part of Article 139 fails to meet this proportionality standard and is unconstitutional on the grounds of “void for unnecessary."