According to Article 73 of the Constitution, although taxes, fees, duties, and other such financial obligations can only be set by law, the executive authority shall be authorized to change the rates in such areas within the upper and lower limits specified by the law. On the other hand, pursuant to paragraph 2 of Article 167 of the Constitution, the executive may be empowered by laws to impose additional financial impositions for imported goods in order to regulate the foreign trade for the benefit of the country’s economy. In the study, additional Customs Duty imposed by the Decree No. 2015/7713 of Council of Ministers, claims during judicial process completed with the decision No. 2017/6611 of The 7th Chamber of the Council of State and the approval decision No. 2018/946 of Assembly of Tax Courts on request of appeal, the defense of Ministry of Economy and judgment of the Court, the principle of legality of tax and the scope of the exemptions regulated in the Constitution on the basis of legal regulations under the issue were examined. In this context determinations made in the trial process and regulations on which those were grounded, especially “additional customs duty” conceptwhich is subject to proceedings, the scope and the legal nature of this concept, the decision of the court through some exemplary regulations of the executive has been criticized and evaluated as a result.