Roman law was a secondary source that was applied only when local customs and laws on a particular subject were lacking. But after a while, local law was also interpreted and evaluated mainly on the basis of Roman law, as it was a kind of common European legal tradition, thus affecting in turn the main source of law. Finally, the work of glossators and civil commentators has resulted in the elaboration of a common law and letter on law, a common legal language and a common method of teaching and science, all qualified as common or common law in Europe, consolidating canon law and Roman law and, to a certain extent, feudal law. Some topics are chosen by the Commission, others are discussed by the General Assembly. .