I think the paramilitary reference was more along the lines of the French Gendarme(?). National Police if you will. The US have no equivalent to those. The rest of the world, on the other hand, does. Militias and Irregulars to me are part of the Infantry Category. I'm not sure if there is enough of a distinction to make a difference for a new Category.

Reserves certainly shoulcn't count as paramilitary. However some paramilitary groups do serve their own country-groups that are independant of the normal military structure yet doing duty for their country of orgin. A classic example was Air America. Others include the German Freikorps and of course the privateers back during the age of sailing warfare. In time gone by most armies were an amalgamation of this and in fact the European professional armies today were originally just a sum of the paramilitary bands that happend to have a permanent contract with a given monarch.