The Livre de Jostice et de Plet, a legal textbook, explains what to do when the shit hits.*
BOOK XIX, CHAPTER XVII
1. Vile filth is indeed a misdeed when one flings it without reason. Vile filth is that which is so stinky that it corrupts the air; and that which is otherwise does not constitute it, if one could keep it at home until the next day.
2. He who throws filth on a man ought to make amends.
3. One may ask: if one has thrown filth on a man, are there grounds for trial by combat (point de gage)? And the response is that if a little bit of filth is thrown, and does not draw blood, or injure, or maim, or cause more than five sous of damage, there are no grounds for battle and the choice of proof lies with the plaintiff. But if great filth is flung, which causes great damage, or an injury, or a cut which causes great damage, in that case there are grounds.
4. One can initiate legal action against someone who resides in a house [from which poo is thrown anonymously?], but it is not the same as accusing a man.
5. Pierre has thrown some filth on me, by which he has done me injury and ten sous worth of damage; and he saw this. And if he says that he did not see this, I am prepared to show and swear as I ought. And Pierre could counter with such denial and defence as he ought. And one would say that Pierre is liable to bear law and to recognize that it was seen or to counter the charge with battle.
6. Concerning damage, one cannot accuse without guarantors, and with guarantors one can.
*The quick and dirty translation is mine