A more thorough explanation:

Unwritten law refers to a set of laws that are not written down as statutes or ordinances, but are instead based on customs and traditions. This can include case law, which is created through court decisions rather than legislation.

For example, in the common law system, judges often look beyond the written words of a precedent to understand the underlying principles and reasoning behind it. This means that the authoritative rules derived from case law may not be explicitly written down, but are instead discovered through the use of reason.

Another example of unwritten law is the concept of "fair use" in copyright law. While the specific limitations and exceptions to copyright law are written down in statutes, the application of fair use is based on a set of unwritten principles that have developed through court decisions over time.

Overall, unwritten law is an important part of the legal system, as it allows for flexibility and adaptation to changing circumstances. However, it can also be challenging to navigate, as the rules may not be explicitly stated and can be subject to interpretation.