Then how do we ban private ownership of WMDs?
Are WMD's suitable for use as arms in the context of a well-functioning militia?
If all items which could conceivably be used as weapons were protected by the Second Amendment, the government would be unable to impose tariffs or excise taxes on much of anything. I don't think the Founding Fathers intended to forbid taxes on alcohol on the basis that it could be used in making Molotov cocktails.
WMD's are not Arms. hey are poisons. Except for nukes. Everybody has a right to keep and bear nukes. Seriously. Do youthink all the NRA folks would run out and get their own neutron bombs?
Then how do we ban private ownership of WMDs?
We don't outright 'ban'/prohibit the ownership of anything. -- As per the 14th, our rights to life, liberty, & property cannot be violated without due process. - So instead of fiat [unconstitutional] prohibitions, we reasonably regulate where & how hazardous chemical, biological, & nuclear materials can be used or stored.
Get the principle? -- It works, and has worked, for years. Many private individuals & businesses own/use/store such hazardous materials.
Simple. Just sit at your little keyboard and type, "You can't! It's unconstitutional!". Standard response which doesn't call for any thinking. Idiots.
In actuality, the banning or regulation of any weapon is done at the state level within the limitations of the state constitution. California is FUBAR because their state constitution says nothing about guns. My state, Illinois, is only slightly better.
The federal government has no authority in this area under the second amendment. Any law they pass under the second amendment would only apply to the federal government, not the states, since the second amendment only applies to the federal government.
That's why the federal Gun Control Act of 1968 and the federal AWB of 1994 were passed under the Commerce Clause, not the second amendment.