Laws of Cricket 1947 Code (Fourth Edition) - Law 26
For a delivery to be fair the ball must be bowled, not thrown or jerked; if either Umpire be not entirely satisfied of the absolute fairness of a delivery in this respect, he shall call and signal "No Ball" instantly upon delivery.
1. For a delivery to be fair, the ball must be bowled not thrown; if either umpire be not entirely satisfied of the absolute fairness of a delivery in this respect, he shall call and signal "No Ball" instantly upon delivery. The umpire at the bowler's wicket shall call and signal "No Ball" if, in the delivery stride, the bowler's front foot lands clear beyond the popping crease, or if he is not satisfied that the bowler's back foot has landed within and not touching the return crease or its forward extension.
2. A ball shall be deemed to have been thrown if, in the opinion of either umpire, the process of straightening the bowling arm, whether it be partial or complete, takes place during that part of the delivery swing which directly precedes the ball leading the hand.
This definition shall not debar a bowler from the use of the wrist in the delivery swing.
3. In conjunction with the above, the following conditions shall apply:-
a. The length of the return crease shall be 4ft.
b. The popping crease shall extend 6ft. either side of the line of stumps.
c. The popping crease and return crease shall be re-drawn during each interval.
Notes on Law 26
1. Subject to the provisions of the Law being complied with, a bowler is not debarred from delivering the ball with both feet behind the bowling crease.
2. The striker is entitled to know whether the bowler intends to bowl over or round the wicket, overarm or underarm, right or left handed. An umpire may regard any failure to notify a change in the mode of delivery as "unfair", if so, he should call "No Ball".
3. It is a "No Ball" if the bowler before delivering a ball, throws it at the striker's wicket even in an attempt to run him out (see Law 46 Note 4 (vii)).
4. If a bowler break the near wicket with any part of his person during the delivery, such act in itself does not constitute a "No Ball".
5. The umpire signals "No Ball" by extending one arm horizontally.
6. An umpire should revoke the call "No Ball" if the ball does not leave the bowler's hand for any reason.
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