The Constitution in Article I Section 8 gives Congress the power to organize and discipline the militia. Under the militia system of the Second Amendment, many weapons were not kept by individuals at homes or business because they weren't considered appropriate for common use.
Today large magazines don't seem appropriate for common use. Under the militia system, they should thus be stored under lock and key at an armory. We don't have armories, but gun clubs and shooting ranges are similar: they can store weapons, and they are suitable for practice.
So Congress doesn't have to take large capacity magazines away from their owners, if they define them as not for common use, and require them to be stored at a gun club, and used only at a gun club or in competition.



