For controls on this to work, there would have to be a treaty governing development among the big nuclear powers —then they with their big sticks dictate the rules to the rest.
In the vacuum of that everyone will feel they have to develop or get left behind.
Additionally something like this (the enabling of political “decapitations”) is only seriously countered by MAD. So nothing would keep Colombia from developing their own and taking out Maduro for example if they were reasonably sure a better alternative would rise in VZ.
More worryingly: Daesh, Baruch Goldstein's fan club, the next Anders Breivik, the janjaweed, Boko Haram, Voluntad Popular, antifa groups, the collectively fired Minneapolis Police Department, the Hells Angels, MS-13, etc.
They could be used by the US, Russia, China, India, Pak, Israel to “decapitate” “rouge” regimes incapable of retribution.
Mexican and ukranian drug orgs? maybe crude non hypersonic for whatever political purpose.
Or imagine the ndraghetta having the crude variety during the time they tried offing magistrates quicker than the state was able to convict the perps... or the Italian red brigades...
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