Some violence against children and teenagers is rooted in laws and regulations, which can be called legal violence. Legal violence means violence that is imposed on children and adolescents in the name of law and by the legislator. One of the cases that is considered legal violence against teenagers is the punishment of people under 18 years of age. In Article 91 of the Islamic Penal Code of 2012, in minimum compliance with international documents, the Iranian legislator required maturity, sound reason and criminal competence for sentencing offenders to Hadd & Qesas. But the serious ambiguity that exists in the above-mentioned legal article is that: Are criminal growth and intellectual perfection in adults under 18 years of age assumed or not? Because in the first assumption, the accused must prove that s/he is not mature, but in the second assumption, the proof of the contrary is up to the accused or the prosecutor's office. In this article, while expressing different views, the authors have reached the conclusion that although the appearance of Article 91 of the Criminal Code requires maturity and criminal competence for juveniles responsibility, but in fact, it implies that they are not criminally competent, unless it is proven otherwise; because otherwise, while promoting a kind of legal violence against teenagers, it is concluded that the legislator has not followed a discriminatory policy regarding adults less than 18 years of age.