I believe it's something the government can do. I remember having discussions about that in journalism classes. As mentioned above, if the government isn't stopping you, then who has that power? If one publisher or theatre refuses to present certain works, the party wanting it presented has the right to have it put on somewhere else. Or to create his or her own forum for it. If it's being censored, then the government's saying you don't have the right to present that.

Having put in my two cents, I'll now look at the definition linked above.