I am talking about non-military groups that function almost like a military. Examples include heavy riot police, police-commanded shock troops, police tactical units, etc. The official army is not involved.
This is definitely not military_service=gendarmerie by virtue of not under command of the national army.
Then, should these still be tagged like landuse=military or amenity=police? I see we have a very rarely used military_service=paramilitary (taginfo); is this a good choice to indicate paramilitary bases?
For this discussion, we will just assume it is legal to map such bases in OSM.
Note: this question intends to query the global practices, and is not limited to only the UK.
Not sure how much insight there is to be gained from a global query for a single tag related to paramilitary organizations. For one thing, the facilities for governmental paramilitary organizations probably should be distinguished from private non-governmental paramilitary organizations.
Here in the U.S., we use the military tagging scheme for military bases plus national and state reserve bases. I’m pretty sure that any other government-run facility would fall under the police tagging scheme. Lots of police departments operate surplus military equipment, even in small rural towns, but this doesn’t really factor into it.
I’m not sure how we’ve been tagging private militia compounds, to the extent we even know about them.
ICE is a civilian agency, despite all the tactical gear, so their offices are tagged as police stations or sometimes just as immigration offices. (Personally I’d consider office=governmentgovernment=immigration to be more appropriate for CIS offices.) I don’t know of any ICE “bases”, but their detention centers are tagged as prisons.
My reading of the amenity=police wiki page, particularly the “by country” section, is that these forces are generally tagged as police. A country-specific operator tag is often used to distinguish between different police forces or groups, including military-style ones. Also tags such as police=barracks can be used to further specify police facilities that are not standard police stations open to the public.
landuse=military is simply a common mistake. It should be ignored.
As police= has =naval_base already, =base could be natural to follow military= features. Or simply uses =barracks first. service_branch= (specializations, not different forces) from military= is agnostically named, and might be used on police