The “rule of four” is the Supreme Court's practice of granting a petition for review only if there are at least four votes to do so. The rule is an unwritten internal one; it is not dictated by any law or the Constitution.
The rule of four is used to prevent a majority of the justices from controlling which cases are heard by the Court. By requiring at least four justices to agree to hear a case, the rule helps ensure that cases chosen for review have the support of a significant portion of the Court. This helps to promote fairness and ensure that cases are not decided by a small, potentially biased group of justices.
The rule of four does not guarantee that a case will be granted review by the Supreme Court, as there are still many cases that are denied review despite support from four justices. However, it does serve as a useful mechanism for filtering out cases that may not be suitable for review by the Court.
Overall, the rule of four plays an important role in maintaining the integrity of the Supreme Court's decision-making process and ensuring that cases are carefully considered before being heard by the highest court in the land.