Art 2 (executive), Sec 2: The President shall be Commander in Chief of the Army and Navy of the United States, and of the Militia of the several States, when called into the actual Service of the United States;
The issue for me isn't what should be. The issue for me is the above language in the constitution.
I'm no constitutional scholar, but I don't see anything about the militia being voluntary in the language. While I might want it there, I don't see it there. That absence of language seems to grant definitional power to the several states from whom the militias will be called out.
Here are the other appearances of "militia" in the constitution. Again, I see no language that says the militia is voluntary.
The fifth amendment says no one can be deprived arbitrarily of "liberty." All that's required to actually deprive one of liberty is "due process of law." The clause indicates it's speaking of criminal proceedings, however.
Art. 2, Sec 8 -- 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;
Amendment II - Right to bear arms. Ratified 12/15/1791. Note A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.
Amendment V - Trial and Punishment, Compensation for Takings. Ratified 12/15/1791. No person shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a Grand Jury, except in cases arising in the land or naval forces, or in the Militia, when in actual service in time of War or public danger; nor shall any person be subject for the same offense to be twice put in jeopardy of life or limb; nor shall be compelled in any criminal case to be a witness against himself, nor be deprived of life, liberty, or property, without due process of law; nor shall private property be taken for public use, without just compensation.
At best, then, it's an issue for State Law as to whether or not Militias should be Compulsory, not a Federal prerogative (in fact, it seems to me this would be closer to Original Intent by far). The Federals can call out the "Militia", but the definition thereof is left to the States.