Sub penalty High school
 

Def player running off the field and the ball is snapped before he gets to his sideline. He is the 12th player. Is this a dead ball foul or do you let the play run and give the O the option on taking the play or the penalty

Live ball illegal substitution foul at the snap, if accepted enforced 5 yards from the previous spot and the down replayed.

so, do not kill the play? at the snap?

See above

It doesn't become a foul until the snap.

Fouls like illegal motion, illegal shift, illegal formation, etc. are live-ball fouls because they can be "fixed" up until the time the ball is snapped.

You are being generous to the defense to call IS. If the defense tried to sub at the last second and sent a player on and immediately the sub tried to leave, it's not IS. It IP, however, I would call the IS because it's 5 yards and IP is 15.

B is not under the same restrictions as A in regards to formations and being between the numbers after the RFP to the snap. They are also not gaining much of an advantage subbing at the last second

In the original post, it is stated he is running off the field so it is apparent he is making an effort to leave. Some wings will even step in if it can put him behind and out of sight and thus avoid the foul entirely.

Yes, it is IS.

It's not IP unless he remains on the field and participates in the play.

Agree. I'm sometimes surprised by how challenging the concept of 'participation' seems to be for some officials.

YEP!! And, if I am a wing official and he is really running hard to get OOB I will give him the benefit of the doubt if he is within a couple yards of the sideline.

Thanks, guys. I was starting to question my sanity there a moment.

Crisis averted.

Canadian Ruling
 

CANADIAN RULING:

Legal, assuming that Team B player's run to the sideline didn't confuse an A player, and B was near the sideline.

On the topic of IS and IP, I have worked with Rs that will take a definitive IP (as in we counted 12 AFTER the play was over) and call it IS because of the difference in the fouls. Why would a R be afraid to make this call?

Because 15 yards is a drive killer, and they are afraid to affect the game.