Through the 2019 Heonma 534 Decision in the Constitutional Court’s Sentence on Nov. 25, 2021, it made the unconstitutional decision as saying of violating the freedom of political expression and the freedom of association in the claimant, a public service worker, because of being contrary to the principle of clarity, etc. regarding the section about 'act with political purpose such as joining other political organizations out of Article 33, Paragraph 2, Text No. 2 in the Military Service Act (amended by Act No. 11849 on June 4, 2013). Here, the aim was to consider concerning the judicial decision made by the Constitutional Court in relation to this case focusing on the guarantee of the freedom of political expression in social service personnel performing mandatory military service and on its limitations in reference to this case. First of all, through the 2016 Heonma 252 decision in the sentence on Oct. 27, 2016, the Constitutional Court has already made the decision of constitutionality as for ‘whether or not the freedom of the election campaign’ in a public service worker in the same article with object to adjudication. Based on this decision, it clearly identified that a public service worker has the public status equivalent to that of a public official as a person of performing public duty and has the political neutrality in light of its position and duty, along with the meaning of a public service worker. In sequence, through 2016 Heonma 252 that is the decision of this case, it examined with regard to restricting ‘political party’ affiliation out of Article 33, Paragraph 2, Text No. 2 in the Military Service Act as the article with object to adjudication. There was also an objection that the complete ban on the political party membership goes against the principle of excess prohibition in consideration of what the claimant in this case is a social service worker and of the characteristics of the duties in public service workers. However, taking into account the characteristics of the status in social service personnel fulfilling their military service obligation and the relationship with other military service performers, it agrees to what the Constitutional Court's decision as saying of not infringing on the freedom of political expression and the freedom of association is reasonable even if applying the principle of excess prohibition, which is the standard for examination. And then, it observed carefully concerning ‘Act with political purpose such as joining other political organizations, etc.’ out of Article 33, Paragraph 2, Text No. 2 in the Military Service Act as the article with object to adjudication in 2019 Heonma 534 that is the decision of this case. Like modern society, guaranteeing the freedom of political expression, which is the basis of democracy, is an important right that must be assured preferentially in the relationship with other fundamental rights, should be deliberate when trying to limit these rights, and needs to be clearer in the case of penal provision. In this sense, ‘other political organizations’ and ‘act with political purpose’ violate the principle of clarity and may not be definite even by the supplementary interpretation of the law enforcer. Thus, the Constitutional Court's decision on unconstitutionality was confirmed to be a desirable direction even for laying down a more accurate regulation.