The judiciary is a branch of government, consisting of justices, judges and magistrates among other types of adjudicators. The primary function of the judiciary is to adjudicate legal disputes. The judiciary is also responsible for interpreting the law, but while in some legal systems this is a fundamental principle (e.g. common law jurisdictions), in others the primary responsibility for interpreting the law belongs not to the judiciary but to the legislature — traditionally, civil law and socialist law jurisdictions — although even in them, the judiciary inevitably must play some interpretive role, since interpretation of the law is an inseparable part of adjudicating legal disputes. This difference can be seen by comparing the United States and People's Republic of China — in the United States, the Supreme Court is the final authority on the interpretation of the law; in the PRC, the final authority on the interpretation of the law is the National People's Congress.
The idea found in civil law and socialist law that the judiciary does not interpret the law has its origins in both in Roman law times. It is said that Justinian had the Corpus Juris Civilis compliled and all other decisions by jurists burned to create certainty in the law. Again in the 19th century French some legal scholars at the time of the development of the Code Napoleon advocated the same kind of approach — it was believed that since the law was being written down precisely, it should not need interpretation; and if it did need interpretation, it could be referred to those who wrote the code. Napoleon, who was an advocate of this approach felt that the task of interpreting the law should be left with the elected legislature, not with unelected judges. However, in practice, this idea was found difficult and judges in France and other countries that Napoleon had conquered or where there was a reception of the Civil Code approach judges once again took on an important role like their English counterparts. At present in civil law jurisdictions in practice judges interpret the law to about the same extent as in common law jurisdictions – though it may be acknowledged in theory in a different manner than in the common law tradition which actually saw judges making the law. In France, the jurisprudence constante of the Cour de cassation or the Conseil d'État is equivalent in practice with case law. In civil law jurisdictions the role of interpretation has taken a much more conservative approach and when the law fails to deal with a situation, doctrinal writers and not judges call for legislative reform, though these legal scholars sometimes influence judicial decision making. Civil law judges also refer to the interpretation of codal provisions and they look for an underlying rationale not only in the particular text, but its relationship to the whole structure of the code as an organizing structure that reflects order in a civil society.
Socialist law adopted the position of civil law, but added to it a new line of thought derived from Communism — the interpretation of the law is ultimately political, and should serve the purposes of Communism, and hence should not be left to a non-political organ (even though in practice, the judiciary was not much of a non-political organ).