I think it may be possible to prevent the development of this technology, at least for several decades until countermeasures can be devised. The microprocessors in cell phones are inexpensive and can be mass-produced by the millions, but there are only a few factories where they are fabricated. These factories are expensive and can be monitored. Drones with built-in GPS capabilities nowadays are programmed for no-fly zones in places like Washington DC. I do not think that even a skilled expert could change this internal programming. The electronics for all of these drones are manufactured in only a few factories, all in China I believe.I expect the Chinese government would cooperate if we asked them not to produce autonomous robot killing drones. It is in their interest not to allow such technology.
Decades from now it might be cheaper and easier to produce sophisticated microprocessors, but as I said by that time I hope we can produce countermeasures. This is discussed in Martin Ford's new book, "Architects of Intelligence," which I am reading.

