I keep talking about the law, but where does the law come from? It comes from a number of sources, and these sources can be ranked in order of importance.
The most importance sources of law are constitutions, not only of the United States, but also of the states. Because of the Supremacy Clause of the U.S. Constitution, the U.S. Constitution has greater importance than state constitutions. Constitutions are the basic organizing document of their respective governments. They define the extent of the authority of government.
Documents such as city charters are like constitutions in that they are basic organizing documents, but they are generally creatures of state law (that is, they are authorized not by the people, but by a higher legal authority), and thus do not have the type of weight that constitutions have.
The next most important sources of law are statutes. Statutes are laws passed by a legislature, such as the United States Congress, or the New York State Legislature, and signed into law by the President of the United States or the governor of a state. Again because of the Supremacy Clause, federal statutes carry more weight than state statutes, and even state constitutions. If a provision in a federal statute conflicts with a provision in a state constitution or statute, the federal statute prevails. This rule is called the Doctrine of Preemption.
Many local governments also have legislatures, and these local legislatures also pass laws, called ordinances. Although I do not want to minimize the importance of local ordinances, particularly in the case of New York City ordinances because they affect so many people, ordinances carry far less weight than federal or state statutes, and when they conflict, the federal or state statutes will usually prevail.
The next most importance sources of law are rules and regulations. Rules and regulations are generally written by government agencies under authority granted to the agency by the legislature in a statute. The rules and regulations written by the agency interpret or implement provisions of a statute. The degree of importance of a set of rules or regulations generally depends on the degree of authority conferred on the agency by the legislature.
The next most important sources of law are the decisions of courts. In part, how important a court decision is depends on the importance of the court. Thus, a decision of the U.S. Supreme Court carries a lot more weight than the decision of a landlord-tenant court judge in District Court, Nassau County.
Decisional law can be looked at in two groups. The first group consists of decisions interpreting other sources of law. The importance of a particular decision depends, in addition to the importance of the court issuing the decision, on the importance of the law being interpreted. Thus, a decision interpreting a provision of the U.S. Constitution is generally a lot more important than a decision interpreting a regulation of a New York State agency.
The other group of cases is generally referred to by attorneys as the common law. It is basically judge made law. Many important parts of the law started as judge made law. For example, the entire field of negligence started as judge made law. On the basis of facts presented to a judge long ago, that judge decided that one party, the defendant, owed a duty of care to the other party, the plaintiff, the breach of such duty of care making the defendant liable to the plaintiff in damages. These days, however, the duty of care owed in a particular situation is often defined not by judge-made law, but by a statute. For example, in automobile accident cases, the duty of care owed by drivers to other drivers and the general public is usually defined, in New York, by the Vehicle and Traffic Law.
The last generally applicable sources of law are learned treatises. Sometimes, a legal scholar summarizes the law so effectively that the pronouncements of the scholar regularly becomes the basis on which courts decide cases. The treatise might be a book or set of books, or a single law review article. After a while, the treatise starts to become irrelevant because the proposition offered in the treatise is repeated so often in decisional law that the decisional law takes over.
There is one more source of law, but this source has narrow application. This source of law consists of private agreements. Contracts are a source of law, but applicable only to the parties to the contract. Nonetheless, it is a source of law that courts will enforce..