Police are policing the scene.
Police are controlling a protest.
Not all scenes are protests, so we don't know that they are controlling a protest.
exists e1 x1 x2.(n_scene(x2) & Theme(e1,x2) & Actor(e1,x1) & v_police(e1) & n_police(x1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_control(e1) & n_protest(x2) & n_police(x1))