Easy to understand portion. Militia refers to State Militias of which all States retain the right to have and some do. The National Guard is not a Militia it's a federally funded, federally controlled etc. reserve component of the federal military. States may not deny their use when fully federalized. That move was part of stripping checks and balances. A few times Governors said no and immediately they had beaucoup problemas with federaerlly funded everything which brought the unions down down on the Governor immediately. All those attempts failed. Many in the west were professional fire fighters. During forest fire season the NG members went for the high paying US Forest Service Jobs. When units were asked to provide and activate members of the guard to drive NG/federal trucks or work in NG/Federal mess tent operations etc.we typically sent back not available notices but that was the only way to evade federal service. The feds never did figure out you caught the biggest groups at scheduled drill weekends.
Come Kuwait and later it all changed. But I know one state that had to strip three battalions to provide one battalion. the attitude was I didn't join the guard to go to real war. 1992 or so things changed. Some units were good some useful only as replacement depot for individual assignment and mot were not equipped nor trained.Some were and performed brilliantly. At no time were the State Militias called up. Reason. Age. They were typically care takers for the empty Guard Armories. One of my last assignments was full time Active Duty adviser trainer. The politics was enough to drive anyone out of those units.