sentences:  The reason is that the free ball was to be treated as the ball on, and one cannot snooker a ball on by another ball on (following the same logic that a red cannot snooker another red when red is on).The only exception to this is when there are only two balls remaining on the table, namely pink and black.If the opposition somehow fouled trying to pot pink, and illegitimately snookered the striker with the black, then it is fair for the striker to snooker the opposition "back" with the free black ball.