https://ihl-databases.icrc.org/applic/ihl/ihl.nsf/ART/365-570030?OpenDocument
It is a Geneva war crime to knowingly engage against an unarmed individual clearly bearing insignia. (Caduceus)
As such, organized groups should condemn the engaging of these personnel under fear of being labeled as terrorists and engaged as such.
Medics are not armed personnel and they should be treated as such - they are of no threat to any individual and there are many other options than killing them. However, NHS are
not trained combat medics and as such, should not be openly given authorization to enter an active warzone. If possible, it could be looked into that a new specialization is brought into the NHS specifically for this role. By all RP standards, they would not be NHS agents but in fact government-supported medical specialists trained in combat medicine.
brb i'll write up a suggestions document.
tl;dr -
no they should not be "allowed" in,
no they should not be punished severely,
yes they can be killed but its' really REALLY bad to do and people really shouldn't do it,
make new rank/specialization for combat medicine (see suggestion document)