The open letter from the Future of Life Institute (FLI) calling for a “ban on offensive autonomous weapons” is as unrealistic as the broad relinquishment of nuclear weapons would have been at the height of the cold war.
A treaty or international agreement banning the development of artificially intelligent robotic drones for military use would not be effective. It would be impossible to completely stop nations from secretly working on these technologies out of fear that other nations and non-state entities are doing the same.
It’s also not rational to assume that terrorists or a mentally ill loan wolf attacker would respect such an agreement.