Eli5: What actually is common law and why is it so important?


So I’ve asked this to hundreds of people and I always got different answers. People seem to celebrate it like it’s this amazing pinnacle of civilisation but their explanations don’t really make it seem that interesting. Idk but any answers will be appreciated 🙂

In: 1

Common law means that law comes from previous decisions…

So you can argue something is not illegal or does not apply based on precedent. Meaning previous cases can be used as arguments in a case.

Compared to civil law where law comes from the law as written. Previous cases do not apply to the way the law is used in this case.

Common law is just a type of legal system based on English law that arose during the Medieval period. In common law, laws come not just from written statutes passed by legislatures, but also from decisions of courts and judges, which we call precedent. The basic idea is that if a court reaches a conclusion in a particular case about what the law actually says or how it applies, the same reasoning should apply to subsequent cases with similar facts. This is opposed to civil law systems, where written statutes are the sole or primarily source of law and previous judicial decisions are of little or no importance. Today, most countries in the world that were formerly part of the British Empire use common law, while most other countries use some form of civil law.

Common law is to be compared to Roman/Civil law (both terminology exists).

In both, laws initially come from the legislative body (congress, …), contrary to for example law systems based on theology.

However, laws as voted by the legislative body never cover all the specific cases. Interactions between multiple legislations might be unclear, and the much various factors shall influence the exact punishment for a crime are also often left unspecified.

Common law recognizes a high level of legitimacy to the judicial system. Decisions made by judges are considered “as good as law itself” (as long as they don’t contradict it, obviously). This means that as time passes, every corner case of the legislation will progressively be covered by case law, and situations in which the behaviour of a law is unclear will become rarer and rarer. In cases of conflict between multiple judicial bodies, the higher ranked one has absolute authority, which is why the supreme court is so important is US politics.

Roman/Civil law does not recognize the judicial body as being legitimate enough to determine once and for all how a voted law should be applied. In practice, that means that a single judge doesn’t get to set a precedent on how to apply a law, but that once the same law has been applied times and times again in roughly the same way, it is expected from judges to continue to follow the precedent. This also means that the authority of higher courts is significantly decreased, as them changing their mind on a subject doesn’t necessarily mean that every lower court has to follow (though they often will). It follows that “supreme courts” in roman law countries are far less relevant politically.

(As a consequence, there is a lot more pressure on the legislative body to actually legislate, by voting new laws or changing the constitution, as the is the only way in Roman/Civil laws to give a clear answer to divisive questions)