Yeah, that's a serious issue. Reminds me of landmines. Almost all the countries who sign up to anti-mine treaties wouldn't use them in the first place, and those who don't sign just ignore it.
Not to say we shouldn't try and do things about mines, clusterbombs and autonomous killer robots, of course, just that it isn't easy.
Landmines is a good reference point in todays technology, and I can see the same end point as well.
I have images of Princess Diana being chased across a field by a terminator type machine, what can I say!