NFHS Rules: Legal vs. Illegal Forward Passes After Line of Scrimmage

Question
When the passer clearly goes past the line of scrimmage and then retreats behind the line of scrimmage and throws a pass, in NFHS rules is this legal or illegal?
The only ruling I can find does is 7-5-1 which descibes a legal forward pass as a ball thrown behind the line of scrimmage..

Answer
I understand where you are coming from with trying to find the exact rule.  I know it is illegal for the QB to pass the LOS, retreat and then throw a forward, but I am looking for the rule.  It would be under the rule where it is illegal to throw a forward pass once they have passed the line of scrimmage.

Under NCAA rules the verbiage is:
"If thrown from in or behind the neutral zone after a ball carrier in possession of the ball has gone beyond the neutral zone."

The NFHS rule is the same, as our the majority of the rules.

Honestly, I would run it by the officials before the game.  Nothing is said about a ball carrier pitching the ball back to someone behind the line of scrimmage.  How do they judge when a back has crossed the LOS on flea-flicker?  Most rules are fully open to interpretation.