The open use of the word "undesireables" by Knight69 is what will throw most people off track. It gives the impression that a "militia" can decide who is acceptable to our society and who isn't- and then to act as they deem fit to change it.
You cannot compare the militias of the 1700's with the definition of militias of today. The former were regulated by the state they served in; that is what I think the founding fathers meant by "well-regulated".
My other point was brought up by someone else. Who would regulate these militias we speak of today? I think by Knight69's definition; (correct me if I'm wrong)they would regulate themselves. Is that a good idea? Would that not lead to outright anarchy?