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. Under the rule, the court can grant review and hear oral argument even if a five-justice majority of the court prefers not to do so. (At the same time, even if four justices are inclined to hear a case, those justices might not vote to grant review if they believe the full court is likely to issue a decision on the merits with which they disagree.) The rule also applies to other actions by the court – for example, the decision to delay action on a petition for review until another case involving the same issue is resolved.