Re: Is this even constitutional?
Who knows what they really mean but this is possibly a case of "impenetrable MoD-speak"
If you look at the blah above the bullet points they are talking about "a soldier in hostile territory" ie someone else's country, and once you go overseas on military operations there are a different set of laws you have to adhere to. The reference to "local authorities" in this case is probably not about the local council but the military/security authority (person in charge) of the area.
The paper could be about a sinister power grab my the military but is more likely to be another example of why normal people should review all documents produced by senior officers before they're released to the press and general public