Seriously? You can't just grab a bunch of people and start declaring things illegal, for example let's say Alex invites 100 random people over in Somewhere, Idaho he and his buddies make a law proclaiming that the democratic republic of the Congo can't have rocks, they proclaim rocks illegal there, they can proclaim it all they want, but it still will not have any authority.
The ICJ is made up of 15 judges elected by General Assembly and Security Council for terms of 9 years. Doesn't sound like random people does it?