Based on Article 190 of the Criminal Procedure Code approved in 2013, which states: “The accused may have one attorney with him during the preliminary investigation stag; it is concluded that the presence of lawyers during the preliminary investigation stage and in order to defend their client should only be with the client , and the absence of the accused will also prevent the acceptance of their representation and the performance of other legal matters. In addition to the fact that this issue is contrary to the concept of the above-mentioned article, it is also being applied in the judicial practice governing. Sometimes it is observed that in the cases presented, lawyers, while appearing without their clients in the investigation departments, request to declare their representation and study the case, and while stating that this is the client’s legal right; they insist on achieving their goal. The main question and challenge of this research is that, considering the above explanation and the application of the provisions in Article 190 of the Criminal Procedure Code and the advisory theory of the Legal Department of the Judiciary; what is the duty of the investigator in cases of encountering similar conditions and whether the order to prohibit the entry of lawyers in the aforementioned conditions is legal or not? In response to this issue, there have been two opinions; first, some who absolutely prevent the acceptance of their representation and registration in the case file until the defendant appears with him, and second, some who, in line with the defendant's legal rights and also observing the principle of interpretation in favor of the defendant, accept such bills and issue permission to read them and simply prohibit them from other legal procedures such as presenting a defense bill, obtaining copies,