The answer is nothing. And the guy in the uniform knows this or else he wouldn't be taking off his uniform and turning off the camera, and he wouldn't care about threatening someone else, cause if it was justified and completely worth it he would have just hit the guy.
But because he wanted to conceal his efforts and draw the guy away from public view, tells you a lot about his intentions and knowing himself what he wanted to do was wrong. He knows he would be in trouble if he got caught. And guess what, he got caught, him and his accomplice.
Litter fining is about keeping the streets tidy, the fine is the deterrant and punishment, not the threat that these goons are gonna gang up on you and beat you up over any other interaction that isn't their business to be doing.