It is banned to use against civilian targets. It's OK to use it against military and paramilitary ones.
No, it is illegal against all targets, military or civilian.
It is known as the Convention on Certain Conventional Weapons, signed at Geneva and entered into force on 10 October 1980.
Which by the way is the same Convention that outlawed land mines and blinding weapons (LASERs). It even put into place other things, like all shrapnel from fragmentary weapons must be detectable through X-Rays (no fragments of glass, plastic, etc). Why do you think nobody but terror groups have used them in over 40 years?