I voted the "I don't know" choice. Ordinarily, it'd be "NFW, Molon Labe" etc.
However,
IF, IF, IF the registration was ONLY of the actual weapon or weapons that were to be used for militia duty (and there'd have to be a yearly training requirement, etc., i.e. a REAL militia as envisioned by the Founders), then I could see it. Go ahead, register the full auto M16 that Uncle will sell me for $750 or so - as long as it is mine, and as long as I can buy whatever I want to buy (esp. including full autos) WITHOUT registration, tax stamps and other such nonsense. Otherwise, FUHGEDDABOUDIT!
You also need fines for being physically unfit for duty (standard to be on a sliding scale, depending upon age) and for failing to properly maintain your weapon, ammo, and other accessories. The Swiss did this (and, I presume, still do), resulting in K-31s that still have pristine bores and which can shoot 2 MOA with iron sights.