Can you have a legal guarding position with a foot out of bounds by NFHS rules?

Please cite rule reference to support your position.

Rule 4-23 Art. 2
There is no reference to being in bounds to have legal guarding position. You only need to have both feet on the floor and the front of the torso facing the opponant.

Kind of playing Devil's Advocate here. Player location 4-35-2 "When a player is touching the backcourt, out of bounds or the threepoint line the player is located in the backcourt, our of bounds or inside the threepoint line, respectively.

Rule 1 calls the court the playing court IE inbounds

rule 10-3-4 (player technical) ...leave the court for an unauthorized reason or delay returning after legally being out of bounds.

I know 10-3-4 is more intended for people running along the baseline or sideline with out the ball and running out of bounds to gain an advantage. It might also apply here, but I would be very reluctant to call it...wow what a can of worms that would be....however since the defensive player is OOB then all the ball handler has to do is hand the ball to them and boom OOB on the defense...7-2-2.....In the case of a dribbler coming up the sideline and contacting the defensive player OOB a pretty good case could be made that the ball probably touched the defensive player and was then dead because it was OOB....

Just some thoughts...I hope we get a good one going on this one...

No need to "hope". It will be several pages long before it's done.

And has been, in the past, as well. :)