Substantive law is the area of the law which concerns the definition of rights and responsibilities. This is in contrast with procedural law, which describes how those rights and responsibilities are enforced. To illustrate an example, laws which define the various degrees of murder are substantive laws, while laws which protect the right to a speedy trial for people accused of murder are procedural laws. Substantive and procedural law are the two main areas of the law, and they are closely interconnected with each other, as one defines the rules of society while the other creates the framework for enforcing them.
The body of substantive law includes things like defining crimes and prescribing appropriate punishments or providing sentencing guidelines which can be used when determining how someone should be sentenced, along with discussions about legal relationships between people as well as entities. People can be given certain rights under this type of law along with responsibilities which they must fulfill, and the law can also define situations in which liability is incurred.
Substantive law includes both civil and criminal law. For example, definitions of torts are an example of this type of law because they deal with describing infractions of the law, determining which actions would be considered unacceptable under the law, and prescribing remedies for tort violations. Likewise, laws against sexual assault and physical abuse are in the criminal code and are additional examples of substantive laws.
Substantive law is usually drafted in the legislature and passed by vote, although there are some regions of the world where laws can be put to a public vote on the ballot. There are also cases in which laws may be repealed because they are deemed outdated or unnecessary. Several governments have embarked on efforts to clear old laws which are no longer enforced from their legal codes for the purpose of making substantive law somewhat more concise and accurate.
In procedural law, rights and responsibilities are not defined, but the law does cover how substantive law is enforced, ranging from protecting rights which people are due under the law to laying out how trials should be conducted. Violations of procedural law can result in questions about whether or not a case was handled justly, and in some cases can cause a verdict to be overturned not because someone is necessarily innocent, but because procedure was not followed. This is one reason why people who work in law enforcement are very careful about following procedure.