There are all sorts of responses to the question “what is law?” One type of law is reasonably easy to identify. Statutes produced by legislatures are definitely laws. But there are other types of law, and the things we call “law” can have varying characteristics. Regulations issued by regulatory agencies can have the power of law, and in a common law system like the U.S., judicial decisions can make new law. Indeed, one of the things that lawyers do in response to rules asserted by opponents is to examine the rule’s pedigree: where did this rule come from, what was the authority of its author, and does it have sway over this case?
A pat response to the question “what is law” is “law is what judges apply to disputes.” This response may work for the incurious layman, but two groups might be left dissatisfied.
First, judges cannot rely on this aphorism. They need to know how to decide what they will apply. Second, those seeking to comply with and utilize the law, including but not limited to lawyers, need to know in advance of adjudication, which rules are part of the system and which are not.
Legal philosophers and social scientists continue to struggle to define law, but a good working definition of law is the following: formal rules that carry the sanction of the state.2 Sure, there are a lot of questions and peripheral issues. What about religious law, or the rules of EBay, or the rules of the National Basketball Association (NBA)?
The answer is that it is good to distinguish between circumstances where these non-state rules carry the sanction of the state and circumstances where they do not. In some places, religious law can carry the sanction of the state, and the rules of EBay or the NBA can take advantage of the power of the state if they are incorporated in binding contracts.