What regulations address being able to use a non-standard/non-DOD M9 range?

For you (ARNG), you need the approval at DARNG level* to use non-DoD property for live-fire events (i.e., weapons qualification).

However, you might luck out and find that the state has already gotten approval for State Police sites (came across them doing that in Virginia).

I see from your profile that you work at the US Marshals Service, so my assumption is that you are referring to using one of their ranges. Unfortunately, if there isn't an agreement already in place between the ARNG and the Marshals Service, you'll have to start from scratch.
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* NGR 385-63 - https://www.ngbpmc.ng.mil/Portals/27/Publications/ngr/ngr%20385-63.pdf

I can't think of anything that references this. I have trained on Law Enforcement ranges before while I was in the national guard. When thinking about military operations can be anywhere. Part of Ranger School is in a national park. For me, it would be incorporated in the DRAW and how you would manage the range as if it was a military range.

I would like to read that regulation. I remember zeroing the old starlight scope in the peak of a clear sunny August day. Put an ammo-can filled with water 100 meters out from the berm. Shoot and spotter corrects, shoot and correct, repeat and hit - Starlight scope is zeroed.
The commander can decide what weight his rank can carry. Doubt any courts-marshal is going to convene from shooting on a civilian range as long as the targets aren't further than 31 meters. After all you're talking about familiarization and qualification not launching to the moon.