Illegal Participation or Illegal Formation or Illegal Substitution.
 

Team A has the ball. A11 comes on field late. Gets set but is not inside the 9 yard mark. If he does not participate is it illegal formation or illegal substitution.

If he does block or participate is it illegal participation.

As long as he is the 11th player or less, its just illegal formation unless you determine it was intended to deceive, which better be pretty obvious to you. If he's the 11th player, set and in formation, what about it would make it illegal participation?

Because.....If he comes into the game in a deceitful manner, it is IP in Fed.

ART. 4 . . . It is illegal participation:
a. When any player, replaced player, substitute, coach, athletic trainer or other
attendant enters and participates during a down.
b. If an injured player is not replaced for at least one down; unless the halftime
or overtime intermission occurs.
c. To have 12 or more players participating at the snap or free kick.
d. To use a player, replaced player, substitute, coach, athletic trainer or other
attendant in a substitution or pretended substitution to deceive opponents
at or immediately before the snap or free kick.
e. For a player to be lying on the ground to deceive opponents at or immediately
before the snap or free kick.

Wrong citation.

7-2-1:
"After the ball is marked ready for play, each player of A who participated
in the previous down and each substitute for A must have been,
momentarily, between the 9-yard marks, before the snap.
PENALTY - Illegal Formation, 5 yards."

If you are deceiving the opponent in this manner, I don't agree...and your citation doesn't back that up, IMO. Let's say all 11 participate in previous play. wide out had a half hearted run block outside and never comes back within the 9's...I'd agree with you.

If A11 comes in off sidelines and you determine it is solely to trick the defense last few seconds before the snap to be uncovered, that is what 9-6-4d was written and intended for.

Reworded by removing a few words: "To use a player.......to deceive opponents
at or immediately before the snap or free kick."

Does anyone have a case book example ?

ILLEGAL FORMATION
7.2.1 SITUATION A: Following a second down play, A89 comes onto the field
as a substitute for A93 but A89 stops 5 yards from the sideline as his team is
ready to snap the ball. Following the snap, A89 goes down field and catches A1's
legal forward pass for a first down. RULING: This is an illegal formation and if the
penalty is accepted it would be marked off from the previous spot. Depending
upon the situation, this could also be illegal participation. (9-6-4d)
7.2.1 SITUATION B: With fourth down and 8 from K’s 20-yard line and K in
scrimmage kick formation, K1 kicks the ball, but at the snap, K had only six players
on the line of scrimmage. After the play is over, R1 throws K2 to the ground
and swings at him. RULING: These fouls would be enforced separately and in
order. R will likely decline the penalty for the K foul so that R will get the football,
and then R’s dead-ball personal foul is then enforced (and R1

I'd advise checking local listings on the whole "get inside the numbers" thing...

Around here, the interpretation is "if Team B knows that they're there, and is covering the receiver, don't flag it if Team A doesn't get inside the numbers".

Luckily, we haven't (yet) had any coaches smart enough to recognize this interpretation, and deliberately "not see/not cover" the receiver who remains outside the numbers between snaps in order to draw a penalty flag on Team A.

Not apples for apples but,


9.6.1 SITUATION D: Between second and third downs, Team A's head coach
sends several substitutes into the game. A11, believing that he has been replaced,
leaves the field and goes directly to his team's box.

Realizing that his position has not been substituted for, A11 enters the field as the ball is being snapped, runs a pass pattern, and catches the ball for a first down.


RULING: This is illegal participation and is marked off 15 yards from the basic spot.


__________________________________________________ __________________________________________________ ____________________

*9.6.4 SITUATION A: Several A substitutes enter the field between downs and go to the team’s huddle, but one replaced player does not leave within three seconds
and is not detected. However, when they break the huddle the replaced player runs toward his sideline and leaves the field just before the ball is snapped.

RULING: An illegal participation foul if the covering official judges that A was using a replaced player or substitute in a substitution or pretended substitution
to deceive the opponents. If not, it is illegal substitution.

COMMENT: It is becoming
prevalent to see more than 11 players/replaced players in a team’s huddle or
in the defensive formation between downs. The replaced player is to leave the
field within three seconds and in such a manner that it does not confuse or
deceive the opponents. (3-7-1)
9.6.4 SITUATION B: Following

Nothing in the OP alleged in deceit. Facts not in evidence.

This.