Perhaps so, but ...

People do manage to murder citizens of powerful nations and get away with it. If you publicize yourself as "Bob the Efreet Trapper" then yeah, war is on. But if all anyone knows is that Fred the Efreet disappeared a few days ago, with no leads, then it's going to depend on whether Fred has enough friends with enough resources to find out what happened and track you down.

Again, assuming the Efreet are not ruling the entire multiverse with their wishes, as (not) seen in most D&D settings.