Rule of four

The rule of four is a US Supreme Court practice that permits four of the nine justices to grant a writ of certiorari.

It has the specific purpose to prevent a majority of the Court's members from controlling their docket.

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] The Rule of Four in general has remained constant for some time in which it takes at least four affirmative votes to grant a petition for certiorari, but the ancillary aspects of it have changed throughout the years, and Justices have not always agreed about these aspects.