A well regulated militia being necessary for a free state...
We can't have well regulated militias without knowing who our gun owners are
You have a point rightwinger. The recording of an
enrolled militia member's name and recording the type and caliber of the arm (singular) he intended to muster with,
is a legitimate exercise of militia regulatory powers (federal and state). It was called the "
return of the militia" . . . essentially a detailed census of a militia company's resources to evaluate readiness -- IOW, information used to help determine if that company was actually "well regulated" (properly functioning / in operational order and condition).
Problem is, there is no current legal purpose or justification for government to record any information pertaining to the identity of a private citizen simply because he owns a gun nor any identifiers pertaining to his personal arms (under the auspices of militia regulation).
To build constitutional legitimacy for a gun registry you would need to reenact a militia law (e.g.,
Militia Act of 1792) that again brings enrolled citizens under the umbrella of federal militia regulations.
Since 1903, Congress has relieved the citizens from any obligation to perform militia duty but it has also extinguished any authority it might claim to have any interest whatsoever in the personal arms of the private citizen (again, under the auspices of militia regulation).