A more thorough explanation:

The Law of Citations is a Roman law that was established in A.D. 426 by Emperor Valentinian III. It listed five juristic writers, including Papinian, Paul, Gaius, Ulpian, and Modestinus, whose works could be cited authoritatively in court.

If a majority of these writers agreed on an issue, the judge was bound to follow the majority view. However, if the writers were equally divided and Papinian (whose view prevailed in a tie) was silent on the issue, the judge could use discretion.

The Law of Citations helped to resolve conflicts in juristic literature and provided a source of principle for judges to base their decisions on.

For example, if three of the five listed writers agreed on a legal issue, the judge would be required to follow their view. However, if only two agreed and the other three were divided, the judge could use discretion unless Papinian's view was known and prevailed in a tie.