Village at Cedar Ridge H.O.A.

I have recently noticed that some inconsiderate individual(s) is allowing their dog(s) to use my front lawn as a litter box. There are at least a dozen ''piles'' in my yard right now. Isn't there a ''rule'' that owners must pick up animal feces after their pets?? What can I do to stop this??? I read a copy of the neighborhood covenant and it says that I am not allowed to put up signs......????