Legal Question in Family Law in California

They can do whatever they want, at least as far as throwing paper, since no DA will prosecute for littering on that situation. Whether it is effective service is a whole other question that turns on all the details of the situation, which you do not provide. The bottom line, however, is that if you lose a dispute over whether service is valid, all you do is delay the inevitable. The target of the service is going to have to deal with the case eventually. If they have notice of the papers and have a defense or response, better to just get on with it.