An American citizen, that is, an American Militia member need not have a "militia leader" until the the militi is called up. And then the leadership is elected by the militia members themselves.
"This concedes that the second is NOT also about private self defense, but about the common defense."
No, the Framers specifically voted down the wording "for the common defence" when constructing the 2A.
"they can say that we are 'unorganized' militiamen, but not the "well-regulated"
Well-regulated means well-skilled. Are your gun sights well-regulated? Is your double-barreled rifle well-regulated?
Here is a citation for you which may explain the use of this term.
From Judge Cooley's Constitutional text
"The right is general. It may be supposed from the phraseology of this provision that the right to keep and bear arms was only guaranteed to the militia; but this would be an interpretation not warranted by the intent. The militia, as has been explained elsewhere, consists of those persons who, under the law, are liable to the performance of military duty, and are officered and enrolled for service when called upon...If the right were limited to those enrolled, the purpose of the guarantee might be defeated altogether by the action or the neglect to act of the government it was meant to hold in check. The meaning of the provision undoubtedly is, that the people, from whom the militia must be taken, shall have the right to keep and bear arms, and they need no permission or regulation of law for the purpose. But this enables the government to have a well regulated militia; for to bear arms implies something more than mere keeping; it implies the learning to handle and use them in a way that makes those who keep them ready for their efficient use; in other words, it implies the right to meet in voluntary discipline in arms, observing in so doing the laws of public order."
The above also addresses your next question...
" When is the last time you were mustered?"
The Framers knew that the militia might be neglected by the legislature but that was no reason to disarm the citizenry. See the words of Richard Henry Lee, George Mason, Patrick Henry, etc.
" it is utterly unavoidable if one concedes the militia clause is a limitation."
The Second Amendment does two things. The first part explains why a citizens militia is needed. It shows the intent of the Framers that standing armies are dangerous to liberty. But the only requirement that the Second Amendment is found in the second half...that "the right of the people to keep and bear arms shall not be infringed."
Richard Henry Lee, who called for and signed the Declaration of Independence wrote the follwing:
"A militia, when properly formed are in fact the people themselves...and include all men capable of bearing arms...To preserve liberty it is essential that the whole body of people always possess arms...The mind that aims at a select militia, must be influenced by a truly anti-republican principle." Federal Farmer, 1788.
Samuel Adams: "The said Constitution [shall] be never construed to authorize Congress to infringe the just liberty of the press, or the rights of conscience; or to prevent the people of the United States, who are peaceable citizens, from keeping their own arms." Massachusetts' U.S. Constitution ratification convention, 1788.
And folks...don't forget the Ninth Amendment as well.
Rick
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"Congress have no power to disarm the militia. Their swords, and every other terrible implement of the soldier, are the birth-right of an American." Tench Coxe 2/20/1788