Neutering animals from people’s yards should be mandatory?

Some time ago a householder dog from District 4, Bucharest, Romania, had estrous and went out on the street and hooked up with another dog. Soon, her puppies will be abandoned in a unknown place (when we asked him what he will do with the puppies, the owner of the female dog said that he knows where to take them). For at least a week we are praying the householder and his wife to give us the two un-neutered female dogs to sterilized them, although they promised to give us the dogs today, today when I went to get the female dog, they were not home. 
We left with the tail between legs and pain in our soul, for the fate of the unborn puppies who will be abandoned on a field by the mean man who is doing this not for the first time. He has five puppies unsterilized and also some unsterilized cats, so will let you to do the calculation. If the two female dogs give birth twice a year to five puppies, it means that only in a year on the streets may occur 20 or more animals, only from the yard of a householder.
On the householder street are another 5 dogs, including two pregnant dog (we saw it today and tomorrow we will try to capture and sterilize them), who are sleeping in the outdoors and get food from the mercy of people. But other people would want then dead.

In conclusion my friends, you think that we will get along well from this situation if the dog and cat owners are not forced by the law to sterilize them?
We are convinced that mandatory sterilization is the only solution that will lead to decrease the number of animals without master.

What is your opinion?

Have you ever noticed your mayor to take action to stop the abandon from private property in the public domain?