all but one ?
 

Is the basic spot for penalty enforcement ever the spot of the foul… ( other than team A's foul behind the LOS )

NFHS rules:
Penalty enforcement is relatively straightforward once you understand a couple of basic principles:
When you have a foul, the first thing that needs to be determined is where the basic spot is located. The basic spot is determined by the type of play (running play, loose-ball play, kick play, etc).

Once you know the basic spot, you apply the All-But-One Principle: All fouls are enforced from the basic spot, except for a foul by the the offense that's behind the basic spot (the but one).

A simple example:
1/10 for Team A at the A-35. Running back A20 runs for 12 yards to the A-47, where he is tackled.

The basic spot in this case is the end of the run (A-47).
All live-ball fouls by Team B are enforced from the basic spot (end of the run).
Any live-ball Team A fouls that occur BEYOND the basic spot are enforced from the basic spot (again, the end of the run).
Any live-ball Team A fouls that occur BEHIND the basic spot are enforce from the spot where the foul occurred.

….. is the enforcement spot at the 5 YL or 25 yl ? I am trying to find a rule or case situation that would enforce from the 25 yl, the spot of the foul.

I'm not sure why my reply went into a "slide" to read the entire post… here is the entire post

LOS is the 50 yl. A1 runs to the 5 yd and is tackled. Prior to being tackled, A2 hits defenseless B1 at the 25 YL. is the enforcement spot at the 5 yl or 25 yl ? I am trying to find a rule or case book that would make the enforcement spot at the 25 .

It's a straightforward all-but-one.

Basic spot is end of run. Foul by A behind basic spot. Enforce from spot of the foul.

It's not "( other than team A's foul behind the LOS )".

It's other than team A's foul BEHIND THE BASIC SPOT.

Because I find enjoyment in such things there are a few apparent, and I emphasize apparent, exceptions.

Example 1: An illegal forward pass thrown from beyond the LOS. One might think that it is a loose ball play and the basic spot is previous, however, this is not a loose ball play, it is a running play, basic spot is the end of the run, i.e. the spot of the pass.

Example 2: KCI. The penalty for KCI includes the specifics provision to award a fair catch 15 yards from the spot of the foul in spite of it being a foul during a loose ball play. (However previous/basic spot enforcement is still an option.)

Roughing the Passer is another exception... it's enforce from the end of the last run, even though it almost certainly happens during a loose-ball play.

No.

Basic spot is:
(1) End of run
(2) Previous Spot
(3) Succeeding spot

Enforcement spot may be the spot of the foul.