Cricket Bowling Action Rules — What Makes a Legal Delivery

Law 24 of the Laws of Cricket governs what constitutes a fair delivery. The core requirement is that the ball must be bowled, not thrown. The distinction matters enormously — a thrown ball can generate additional pace and spin that no batter can fairly anticipate, giving an illegal bowler an unfair advantage.

The Elbow Flexion Rule

In 2004, the ICC introduced a scientifically based standard for measuring bowling actions. A delivery is legal if the bowler's elbow does not straighten by more than 15 degrees during the bowling action — from the point when the arm reaches horizontal to the point of ball release. This 15-degree tolerance accounts for the natural biomechanical flexibility all bowlers exhibit, including the optical illusion of straightening created by arm rotation.

How Illegal Actions Are Identified

The process begins with the on-field umpires, who have the authority to call a no-ball if they believe a bowler throws the ball. However, since it is nearly impossible to determine elbow flexion with the naked eye at match pace, umpires typically report a suspected action to the match referee rather than calling it in the moment. The match referee then formally reports the bowler to their national board and to the ICC.

The ICC Testing Process

A reported bowler is required to undergo a biomechanical assessment at an ICC-accredited testing centre within 14 days of being reported. The test uses high-speed cameras and motion capture technology to measure elbow extension during delivery. If the assessment finds the extension exceeds 15 degrees, the bowler may be suspended from bowling in international cricket until they remodel their action and pass a reassessment.

Notable Cases in Cricket History

The most prominent illegal-action controversy involved Muttiah Muralitharan of Sri Lanka. His unusual wrist action created the visual appearance of throwing. Multiple independent biomechanical tests confirmed his elbow extension was within legal limits — but the controversy accompanied his career throughout. Shane Bond (New Zealand), Shoaib Akhtar (Pakistan), and Harbhajan Singh (India) were also investigated at various points. More recently, Saeed Ajmal and Mohammad Hafeez of Pakistan were reported and required to remodel their actions.

Re-entry After Suspension

A bowler suspended for an illegal action may return to international cricket after undergoing a reassessment that confirms their revised action is within the 15-degree tolerance. They may continue playing in domestic cricket during the suspension, though they cannot use the reported delivery type (e.g. if their doosra was reported, they must not use it at domestic level until cleared). Most bowlers who remodel do return successfully, though some lose effectiveness after the change.