Chemical weapons are banned because they kill indiscriminately, and it causes undue suffering compared to conventional weapons, not because you can mass produce them. Drones wouldn't have either of those issues.
Flying land mines can be equally indiscriminate. Especially if you set the targeting to an ethnic group. These are explosives so they won’t always kill their target, they’ll do a lot of maiming and anyone standing near the target will be on the receiving end too.