Legal security is one of the most important foundations for building a state of law in which all public powers are subject to the law, and legal security is one of the most important goals that the law aims to achieve, and the concept of legal security is devoted to the need for public authorities to achieve a measure of relative stability of legal relations And a minimum level of stability for different legal centers; With the aim of spreading security and reassurance between the parties to legal relations from public and private legal persons; So that these people can act in confidence on the guidance of the existing legal rules and regulations at the time of carrying out their activities, and arrange their conditions in light of them without being exposed to surprises or sudden actions, issued by the public authorities that would undermine this reassurance or storm this stability, as if issued by the judiciary Constitutionalism in the field of subsequent oversight of the constitutionality of laws by virtue of the unconstitutionality of a legislative text having retroactive effect. The importance of the role of the Supreme Constitutional Court in protecting the principle of legal security is evident through the appeal lodged with it due to sudden changes or amendments that threaten the rights and freedoms of individuals, although the Egyptian constitution did not explicitly stipulate the principle of legal security, the Supreme Constitutional Court applied it In many of its provisions drawn from many of the constitution’s texts, it ruled, accordingly, that some legislative texts in the non-criminal field that were applied retroactively were unconstitutional, and it was decided that the constitution, although originally authorized by the legislator, had a retroactive effect of non criminal legislative texts However, the legislator’s authority in this field is not absolute, and judiciary in this sense is the ultimate guarantor of the rule of law, because legal security is one of the most important elements of a modern legal state based on the rule of law. Given that the provisions are applied retroactively, and this is inconsistent with the principle of legal security, which requires the stability of legal centers and not to be disturbed, the role of the Supreme Constitutional Court has emerged to ensure that legal security and the balance between the principle of reaction and the principle of legal security are achieved.