Really? So what is the proscribed militia weapon? What would they decide that on? Don't say musket, they are no longer in "common use".
The state would testify. It's their call and no one elses.
They have the responsibility to form a Militia. If the state says they intend to arm their Militia with 6" shotguns, then the federal government may not infringe on the availability of that weapon. Doing so would infringe on the ability of a state to form their Militia, a violation of the second amendment.