This happened in the A&M-Missouri St game this weekend. I'll walk through the rules as an exercise for myself.
6-3-8 If a scrimmage kick (other than one that scores a field goal) goes out of bounds behind a goal line, the ball becomes dead and belongs to the team defending that goal line.
8-7-2-a The impetus imparted by a player who kicks, passes, snaps or fumbles the ball shall be considered responsible for the ball’s progress in any direction even though its course is deflected or reversed after striking the ground or after touching an official or a player of either team (A.R. 6-3-4-III; A.R. 8-5-1-II, VI and VIII; and A.R. 8-7-2-I-IV).
b. Initial impetus is considered expended and the responsibility for the ball’s progress is charged to a player:
1. If that player kicks a ball not in player possession or bats a loose ball after it strikes the ground
2. If the ball comes to rest and that player gives it new impetus by any contact with it, other than through forced touching (Rule 2-11-4-c).
c. A loose ball retains its original status when there is new impetus.
So the punt is responsible for the ball going into the end zone. The muff does not create impetus. There is a live ball in the end zone, touched by Team B in the field of play. Team B kicks the ball on the ground out the back of the end zone. The ball obviously becomes dead when it crosses the end line, and 6-3-8 says it belongs to Team B. Team B ball in Team B end zone with Team A impetus is a touchback. Except we have a foul for illegal kicking.
2-16-1-a Kicking the ball is intentionally striking the ball with the knee, lower leg or foot.
b. A legal kick is a punt, drop kick or place kick made according to the rules by a player of Team A before a change of team possession. Kicking the ball in any other manner is illegal (A.R. 6-1-2-I).
9-4-4 A player shall not kick a loose ball, a forward pass or a ball being held for a place kick by an opponent. These illegal acts do not change the status of the loose ball or forward pass; but if the player holding the ball for a place kick loses possession during a scrimmage down, it is a fumble and a loose ball; if during a free kick, the ball remains dead (A.R. 8-7-2-IV and A. R. 9-4-1-XI).
PENALTY—10 yards, plus loss of down for fouls by Team A if the loss of down is not in conflict with other rules [S31 and S9] (Exception: No loss of down if the foul occurs when a legal scrimmage kick is beyond the neutral zone).
So the illegal kicking did not make the ball become dead, it stayed live until it went out of bounds. And there is a 10 yard penalty for Team B illegally kicking the loose ball in the end zone. But where does it get enforced from?
10-2-1-a For many fouls, the enforcement spot is specified in the statement of the penalty. When the enforcement spot is not specified in the statement of the penalty, the enforcement spot is determined by the Three-and-One Principle.
10-2-2-c-3 The Three-and-One Principle (Rule 2-33) is as follows:
3. When the team not in possession commits a foul either behind or beyond the basic spot, the penalty is enforced at the basic spot.
10-2-2-d-4-b Postscrimmage kick spot, if the foul is governed by postscrimmage kick rules.
10-2-3 Postscrimmage Kick Enforcement
ARTICLE 3.
a. Under postscrimmage kick enforcement rules, fouls by Team B that satisfy the conditions in paragraph b (below) are treated as if Team B had been in possession at the time the foul was committed, even though by Rule 2-4-1-b-3 team possession had not changed.
b. Postscrimmage kick enforcement applies only to fouls by Team B during a scrimmage kick and only under the following conditions:
1. The kick is not during a try, a successful field goal, or in an extra period. (A.R. 10-2-3-IV)
2. The ball crosses the neutral zone.
3. The foul occurs before the end of the kick (A.R. 10-2-3-I, II, and V).
4. Team B will next put the ball in play.
If these conditions are all met, the penalty is enforced according to the Three-And-One Principle. Team B is taken as the team in possession with the postscrimmage kick spot as the basic spot (Rule 10-2-2-c). See Rule 2-25-11 for the postscrimmage kick spot. (A.R. 10-2-3-I-VII)
2-25-11 Postscrimmage Kick Spot
ARTICLE 11. The postscrimmage kick spot serves as the basic spot when postscrimmage kick enforcement applies (Rule 10-2-3).
a. When the kick ends in the field of play, other than in the special cases given below, the postscrimmage kick spot is the spot where the kick ends.
b. When the kick ends in Team B’s end zone, the postscrimmage kick spot is Team B’s 20-yard line.
Special cases:
1. On an unsuccessful field goal attempt, if the ball is untouched by Team B after crossing the neutral zone and is declared dead beyond the neutral zone, the postscrimmage kick spot is:
(a) The previous spot, if the previous spot is on or outside Team B’s 20-yard line; (A.R. 10-2-3-V)
(b) Team B’s 20-yard line, if the previous spot is between Team B’s 20-yard line and its goal line.
2. When Rule 6-3-11 is in effect, the postscrimmage kick spot is Team B’s 20-yard line.
3. When Rule 6-5-1-b is in effect, the postscrimmage kick spot is the spot where the receiver first touched the kick.
8-5-1-b It is a safety when:
b. An accepted penalty for a foul leaves the ball on or behind the offending team’s goal line (Exception: Rules 3-1-3-g-3 and 8-3-4-a) (A.R. 8-5-1-III and A.R. 10-2-2-VI).
So the basic spot is the postscrimmage kick spot, which is B's 20 yard line. The foul happened behind the basic spot, so the penalty is enforced from Team B's end zone. And so it's a safety because it's enforced from Team B's end zone. The approved ruling below is a little different in that the illegal kicking happens in the field of play, which gives new impetus to the ball and directly causes the safety.
Approved Ruling 9-4-4-I. 4/8 @ A-48. From a scrimmage kick formation, A32 punts the ball to the B-7 where it hits B25 on the leg. As the ball rolls along the ground, B25 then kicks it at the B-4 to prevent Team A from recovering. The ball bounces into Team B’s end zone and over the end line. RULING: The result of the play is a safety, as B25’s kicking the ball provides new impetus. Foul by B25 for illegally kicking the ball. Team A may decline the penalty and take the two points, or accept the penalty. The foul by B25 is governed by postscrimmage kick rules, so the accepted penalty would give Team B the ball at the B-2, first down and 10. (Rules 8-5-1-a and 8-7-2-b)
Before Team B illegally kicked the ball, Team A was about to recover the muffed kick in the end zone. This would have been a touchdown.
6-3-3 When a scrimmage kick that has crossed the neutral zone touches a player of the receiving team who is inbounds, any player may catch or recover the ball
6-3-6-a If a player of the kicking team catches or recovers a scrimmage kick that has crossed the neutral zone, the ball becomes dead (A.R. 6-3-1-IV). The ball belongs to the receiving team at the dead-ball spot, unless the kicking team is in legal possession when the ball is declared dead. In the latter case, the ball belongs to the kicking team.
8-2-1-d A touchdown shall be scored when: A free kick or scrimmage kick is legally caught or recovered in the opponent’s end zone.
