Operation of law is a legal fiction that describes how a process, which is sometimes called Black Letter Law.

Many common legal practices are said to work by operation of law.

In marriage, many of the rights and obligations that come to the parties are said to work by operation of law. For example, the practice of a married woman taking the name of her husband works by operation of law. After she marries, a women simply changes her name to her husband’s because the practice and the precedent for doing so have been established. No other action is required of her.