Short answers, pulled from the story.
The judiciary is the system of courts that adjudicates legal disputes and interprets, defends, and applies the law to the facts of each case. Under the doctrine of the separation of powers, it is distinct from the legislature, which makes statutory law, and the executive, which enforces it. Courts with judicial review power can also annul laws found to be incompatible with a constitution, treaties, or international law.
The Corpus Iuris Civilis was a codification of all Roman law completed during the reign of Justinianus in the Dominate period (284-565 AD). It consisted of four parts: the Institutiones, the Digesta, the Codex, and the Novellae. After its rediscovery in 1070, it became the foundation of legal education at the University of Bologna and the basis for the medieval Ius Commune legal tradition across Europe.
Ius Commune emerged around the 15th century as a combination of canon law, which supplied common norms and principles, and Roman law, which provided the actual rules and technical terms. The process it created allowed for appeal and blended inquisitorial elements, where judges investigated evidence directly, with adversarial elements, where parties bore responsibility for presenting evidence.
United States Supreme Court justices are appointed by the President of the United States and confirmed by the United States Senate. They serve a life term or until retirement. The Supreme Court is located in Washington, D.C., and the federal court system it oversees is organized into 94 judicial districts divided into twelve regional circuits.
Japan's judge selection process is longer and more stringent than in countries such as the United States and Mexico. Assistant judges are trained at the Legal Training and Research Institute in Wako and cannot sit alone for five years after appointment. Full judges must have ten years of experience as a public prosecutor or practicing attorney, and Japan's judicial branch includes 438 summary courts alongside the Supreme Court, eight high courts, fifty district courts, and fifty family courts.
Gratian organized the entire body of church law into a text known as the Decretum Gratiani, which became the first part of the Corpus Juris Canonici, a collection of six legal texts. Canonists of the Roman Catholic Church used this collection as their governing legal authority until the 19th of May 1918, when a revised Code of Canon Law promulgated by Pope Benedict XV on the 27th of May 1917 came into force.