It is derived from approved legislation. Common Law was first established in England and practiced primarily in English-speaking countries. A Common Law system is a system formed basically from old or precedent opinions and decisions of judges of higher courts rather than a parliament, which becomes law or a model for all other cases in other lower courts. Sometimes limiting yourself too much to previous cases can lead to bad or unfair decisions. The sources of law in public international law are not much different from jurisprudential law in common law countries, because common law compared to the sources of public international law implements legislation, provides stability and coherence to the legal system, is flexible and allows for changes in the law governs, and with a quicker response than the law made by parliament. However it is very strict, principled, undemocratic as it is established by judges rather than the people, and legislation can easily override it at any time. So, basically, common law is very similar to, for example, customary international law, since it is law enacted by judges making decisions through precedent, where lower courts refer to higher courts, and customary international law is an old set of rules and norms mandatorily imposed by a State on the behavior of its individuals. So they are both flexible systems that depend on the old and