Since when does anyone need authority to confront someone else? If I see someone suspicious in my neighborhood, I have every right to follow the person on a public street, and even walk up to him/her and ask questions. As long as I don't physically assault the person or impede their ability to move, I have broken no law. If that person hits me, then they are guilty of assault, and I have every right to defend myself. But they do not have the right to "defend" themselves from my "confronting" them by attacking me physically.
Not today; if you're white, and they're black.