Answer:
Step-by-step explanation: The rule of four is not required by the Constitution, any law, or even the Supreme Court's own published rules. Rather, it is a custom that has been observed since the Court was given discretion over which appeals to hear by the Judiciary Act of 1891, Judiciary Act of 1925 and the Supreme Court Case Selections Act of 1988.[1]
The "Rule of Four" has been explained by various Justices in judicial opinions throughout the years.[2] For example, Justice Felix Frankfurter described the rule as follows: "The ‘rule of four’ is not a command of Congress. It is a working rule devised by the Court as a practical mode of determining that a case is deserving of review, the theory being that if four Justices find that a legal question of general importance is raised, that is ample proof that the question has such importance. This is a fair enough rule of thumb on the assumption that four Justices find such importance on an individualized screening of the cases sought to be reviewed."[3]
