The Constitution has the following to say about the militia:
The Congress shall have Power To lay and collect Taxes, Duties, Imposts and Excises, to pay the Debts and provide for the common Defence and general Welfare of the United States; but all Duties, Imposts and Excises shall be uniform throughout the United States;
To provide for calling forth the Militia to execute the Laws of the Union, suppress Insurrections and repel Invasions;
To provide for organizing, arming, and disciplining, the Militia, and for governing such Part of them as may be employed in the Service of the United States, reserving to the States respectively, the Appointment of the Officers, and the Authority of training the Militia according to the discipline prescribed by Congress;
That pretty clearly suggests that "militia" is whatever the government argues that it is. It's a thing they organize, arm and discipline it so they can call it forth to execute the laws of the union, suppress insurrections and repel invasions.
The end effect is kicking a big fuckin' hole in the 2nd amendmen.