Patere legem quam ipse tuleris»: from praetorian edict to the European Court of Justice

In a fragment of the libri ad edictum Ulpian (D. 2.2.1 pr.-1) outlines the ratio of the edict quod quisque iuris: the aequitas in mutual relations. The actual ius novum that a magistracy establishes against anyone, he himself ought to employ whenever his adversary demands it. Accursius explicitly relates this edict with the principle «patere legem quam ipse tuleris». In fact, the glossator identified the foundation of the edict quod quisque iuris in the «divine law», according to which «quod tibi fieri non vis alteri ne feceris» and in the decision of great wisdom «in decre. dist. j. c. j. & Cato, Patere legem quam ipse tuleris». As it is common for the CJEU to apply maxims referring to ancient Roman Law, this regula is often referred to a general principle of European Law and it is applied particularly by the judges of the Courts to the decision C-493/17.