Creating Legal Systems - The Art of World Building
Aug 262021

Most of our settings will have a legal system, even if it’s as simple as “an eye for an eye.” This section takes a high level and simplified view of these systems because most world builders will not be writing a legal drama, which is the only scenario where more detail is likely needed. Some places have a mix of the systems we’ll cover, and we can do the same, though we may struggle for a reason to. In our setting, the publication of legal decisions, so that everyone can access them, is required; without this, laws are not enforced equally.

With all systems, our usage is primarily to cause trouble for our characters, who run afoul of a law, either by breaking it, encouraging others to do so, or even just speaking out against it. Any of these are more likely when traveling, due to ignorance of local laws, but there are other factors. Characters are usually on a mission and only passing through, and are therefore trying to avoid trouble, but we can have one member who tends to cause problems and another who knows the local laws and tells them what not to do. Use this as a guide. This helps us add an issue that either develops character(s) or plot.


There are several types of legal systems. The source of laws is one of their primary differences. The system type arguably matters less than specific laws that impact our story, but they are briefly summarized next.

Civil Law

One of the most widespread systems (along with common law), civil law means that a legislature creates and modifies an authoritative source that formalizes laws. That source is either a constitution (at the sovereign power or federal level) or a statute (at a lower level, such as states in the United States). Constitutional law tends to be broad and interpreted more at the statutory level, which is one reason variations can exist between states within a union. For example, as of this writing, marijuana is illegal at the federal level in the U.S. but legal in some states. To do this in our fictional world, we mostly need to know there’s a sovereign power and self-governing bodies (like states or provinces) within it. A character can get themselves into trouble outside their home territory because they didn’t know something legal back home is illegal somewhere else. This can happen within a power, not just when traveling between different ones. If there’s no law we’ve broken when we’re brought before a judge, he has no authority and the case will be dismissed.

Common Law

Common law derives its name from being common across England among the king’s courts, and since Britain’s empire spread far, it is now common across a third of the Earth, too, making it the other most widespread legal system (along with civil law). Its primary feature is that a judge will look to past cases that are like the one presented to him. If similar enough, he must abide by the past reasoning when ruling on the current case, as the precedents are considered the law; this principle is called “stare decisis” and is the main difference between this and civil law. If the case is unique, he will be the first one to rule on the matter, his decision henceforth becoming law to be considered by judges thereafter when faced with a similar case. Because of this, if there’s no law, a judge can effectively make one. This contrasts with civil law, where a judge would have no authority to do anything.

Another name for this is judge-made law or judicial law.

Religious Law

If there’s a religious document, such as the Bible or Quran, this will be the source of religious law. Either a god or a prophet (through whom they spoke) may be considered the author of the document, and this sometimes results in the ideas being named accordingly; Mosaic laws were written down by Moses, for example. Such sources are considered the word of a god about ethics and morality. A famous example may be the Ten Commandments. Variations are considerable across religions, which gives us flexibility and frees us from “getting it right.” Canon law is the body of laws and regulations that a religious authority creates; these are typically named after a source, such as apostles or a church (or a group of them). As with seemingly everything in religion, these teachings can be interpreted quite differently, resulting in sects and other divisions within the religion, each adopting and applying their own laws. Past cases may or may not be considered; the interpretations of mankind are less important than the word of a god.

Contrasting Types

Both civil and common systems are unlikely among civilizations that have no written language or which are nomadic, due to the inability to codify the laws or a library in which to store them for reference. Expecting someone to memorize so much is improbable and prone to error, but maybe we have a trusted species with perfect recall or the ability to summon knowledgeable spirits from the afterlife as needed. Without such measures, only civilizations that have advanced to and beyond Roman or medieval may reasonably be assigned either legal system. We might see elves and dwarves with such a system in fantasy, but probably not ogres and goblins.

By contrast, religious systems may be heavily dependent on fewer texts (at least in the beginning), which are readily available in churches, with the laws implied or explicitly stated in sermons and other stories that practitioners regularly hear. While not a rule, a religious system may be likely before and during more sophisticated civilizations.

A character who understands the difference between common and civil systems might have a different reaction to being accused of a crime. If he’s aware there’s no law and finds himself before a judge in a civil system, he might be unconcerned because the judge can’t do anything to him. The case will be dismissed. But if he’s in a common law system, the judge can invent the law based on this case. He might not feel so confident. In a religious system, it could go either way.

Civil judges must consider any previous cases (known as case law), but this is secondary to interpreting the source of law (constitution or statue). By contrast, in common law systems, previous cases are the law the judge is following, and he is highly reluctant to go against precedent.


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