It's kind of funny. I see the concept of a federal paramilitary Gendarmerie is more prevalent in southern civil code jurisdictions (those that spent a fair time under Roman rule) while the northerners, in general, seem to shy away from that and draw a more distinct line between the military and the police.
I expect
@Kirkhill can give us a historic foundation for that
I'll try.
The English Civil War saw people distrust both the King's troops and Cromwell's Major-Generals.
The Bill of Rights of 1689 explicitly condemned James VII and II for raising a standing army without the consent of parliament. It also addressed billeting troops in pri ate residences.
These, along with depriving citizens of arms and the means to defend themselves, were all measures that Brits (English, Scots, Welsh and Irish) associated with heavy-handed pacification efforts across the Isles. That attitude was carried with the Brits, Huguenot French and Palatine Germans who established the colonies that became America.
These people had been subject to extra-judicial killings, field punishments, investments by the Highland Host and French Dragoons, slaughter in the fields while at church service, forcibly impressed into foreign armies, local mines and salt works, and to plantations in Ireland, Newfoundland, New England and the West Indies.
In short the populace did not trust authority with a gun.
Thus the unarmed citizen police.
Guns and Marines on ships to keep tbe borders secure and to rule the waves? Perfectly acceptable.
Peterloo Dragoons beating striking rabble from horseback and sending them to Australia? Not having it.
As to the rest of the northerners - some writers will note the overlap of Anglo-Saxon Witans and Norse Althings and the importance of the Hundreds councils and the Fyrds or citizen army.
Justinian and Carolingian law never gained the ascendancy in the seagoing northern communities that it did among the farmers of the continent despite the efforts of Alfred of Wessex.
He carried England south of the Thames. The rest of Britain, including Ireland, along with Scandinavia, the Faroes, Iceland, Greenland, as well as Newfoundland, Labrador, and conceivably Baffin and Oak islands, were all subject to Danelaw.
It is hard to catch a man on a boat to whip him into shape.
Farmers are much easier to grab.