Insein said:
I always thought the ball could not advance on a fumble. Keeps the old fumblerooski play from happening.
These plays should be one of two things. A TD because it broke the plain or a fumble out of bounds and the ball returns to the spot where possession was lost. It's really that simple.
As Arodin mentioned.
That rule is only at certain times
ARTICLE 5. FOURTH-DOWN FUMBLE
If a fourth-down fumble occurs during a play from scrimmage:
The ball may be advanced by any member of the defensive team
The player who fumbled is the only Team A player permitted to recover and advance the ball.
If the recovery or catch is by a teammate of the player who fumbled, the ball is dead, and the spot of the next snap is the spot of the fumble, or the spot of the recovery if the spot of the recovery is behind the spot of the fumble.
Note: After a change of possession has occurred, the restrictions in (b) and (c) are no longer in effect for the remainder of the down.
ARTICLE 6. FUMBLE AFTER TWO-MINUTE WARNING
If a fumble by either team occurs after the two-minute warning:
(a) The ball may be advanced by any opponent.
(b) The player who fumbled is the only player of his team who is permitted to recover and advance the ball.
(c) If the recovery or catch is by a teammate of the player who fumbled, the ball is dead, and the spot of the next snap is the spot of the fumble, or the spot of the recovery if the spot of the recovery is behind the spot of the fumble.
Note: The restrictions in (b) and (c) are applicable during a Try throughout the game.