I didn't know any man could carry an ICBM, SLBM or long range bomber, yet those have been the subject of "arms" control treaties. As have battleships, cruisers,etc. (That sort of "arms control" never has worked for long either).
Those are examples of the increased vagary of what was a clear term. Arms were initially only those things which could be carried in the arms. Expanding that umbrella was never the Founders' intention merely that of Sophists.
Negoiation between nations regarding these weapons is not relevent to the 2d.
Nor did they intend that Private armies be raised and armed.
Ask Aaron Burr about Jefferson's view of THAT.