Here is the rule according to IBSF!!
Mike
http://www.ibsf.info/rules-snooker.shtml#3_10
14. Foul and a Miss
The striker shall, to the best of his ability, endeavour to hit the ball on. If the referee considers the Rule infringed, he shall call FOUL AND A MISS unless only the Black remains on the table, or a situation exists where it is impossible to hit the ball on. In the latter case it must be assumed the striker is attempting to hit the ball on provided that he plays, directly or indirectly, in the direction of the ball on with sufficient strength, in the referee's opinion, to have reached the ball on but the obstructing ball or balls.
(a) After a foul and a miss has been called, the next player may request the offender to play again from the position left or, at his discretion, from the original position, in which latter case the ball on shall be the same as it was prior to the last stroke made, namely:
(i) any Red, where Red was the ball on,
(ii) the colour on, where all Reds were off the table, or
(iii) a colour of the striker's choice, where the ball on was a colour after a Red had been potted.
(b) If the striker, in making a stroke, fails to first hit a ball on when there is a clear path in a straight line from the cue-ball to any part of any ball that is or could be on, the referee shall call FOUL AND A MISS unless either player needed snookers before, or as a result of, the stroke played and the referee is satisfied that the miss was not intentional.
(c) After a miss has been called under paragraph (b) above when there was a clear path in a straight line from the cue-ball to a ball that was on or that could have been on, such that central, full-ball, contact was available (in the case of Reds, this to be taken as a full diameter of any Red that is not obstructed by a colour), then:
(i) a further failure to first hit a ball on in making a stroke from the same position shall be called as a FOUL AND A MISS regardless of the difference in scores, and
(ii) if asked to play again from the original position, the offender shall be warned by the referee that a third failure will result in the frame being awarded to his opponent.
(d) After the cue-ball has been replaced under this Rule, when there is a clear path in a straight line from the cue-ball to any part of any ball that is or could be on, and the striker fouls any ball, including the cue-ball while preparing to play a stroke, a miss will not be called if a stroke has not been played. In this case the appropriate penalty will be imposed and
(i) the next player may elect to play the stroke himself or ask the offender to play again from the position left, or
(ii) the next player may ask the referee to replace all balls moved to their original position and have the offender play again from there, and
(iii) if the above situation arises during a sequence of miss calls, any warning concerning the possible awarding of the frame to his opponent shall remain in effect.
(e) All other misses will be called at the discretion of the referee.
(f) After a miss and a request by the next player to replace the cue-ball, any object balls disturbed will remain where they are unless the referee considers the offending player would or could gain an advantage. In the latter case, any or all disturbed balls may be replaced to the referee's satisfaction and in either case, colours incorrectly off the table will be spotted or replaced as appropriate.
(g) When any ball is being replaced after a miss, both the offender and the next player will be consulted as to its position, after which the referee's decision shall be final.
(h) During such consultation, if either player should touch any ball in play, he shall be penalised as if he were the striker, without affecting the order of play. The ball touched shall be replaced by the referee, to his satisfaction, if necessary, even if it was picked up.
(i) The next player may ask if the referee intends to replace balls other than the cue-ball in the event that he should ask for the stroke to be played from the original position, and the referee shall state his intentions.
10. Snookered After a Foul
After a foul, if the cue-ball is snookered, the referee shall state FREE BALL (see Section 2, Rule 16).
(a) If the player next in turn elects to play the next stroke,
(i) he may nominate any ball as the ball on, and
(ii) any nominated ball shall be regarded as, and acquire the value of, the ball on except that, if potted, is shall then be spotted.
(b) It is a foul if the cue-ball should
(i) fail to hit the nominated ball first, or first simultaneously with the ball on, or
(ii) be snookered on all Reds, or the ball on, by the free ball thus nominated, except when the Pink and Black are the only object balls remaining on the table.
(c) If the free ball is potted, it is spotted and the value of the ball on is scored.
(d) If a ball on is potted, after the cue-ball struck the nominated ball first, or simultaneously with a ball on, the ball on is scored and remains off the table.
(e) If both the nominated ball and a ball on are potted, only the ball on is scored unless it was a Red, when each ball potted is scored. The free ball is then spotted and the ball on remains off the table.
(f) If the offender is asked to play again, the free ball call becomes void
