If I may ask, how so?
I could certainly understand with today's 'modern' Constitutional interpretation, but the national defense provision was quite restrictive. Mostly because things like 'border patrol' and implementation of immigration was reserved to the States.
The militias were quite autonomous until a State made a request to the federal government for assistance and the militia, once called up, reached the point of muster. It was only then they were considered as being 'in the service' of the United States. (Houston v. Moore, 1820)
It would seem an elegant and workable solution to me if one were trying to avoid standing armies, but I guess we'll never really know since the idea never had a chance of being tried.
I'm speaking as an engineer here having worked in the defense industry knowing what it takes to build the coordinated communications and logistical infrastructure of a national military. Between 50 State legislatures with 50 command hierarchies, coordinating it all would be a nightmare.