Make junk mail illegal

I live in a block of 19 units and have a "No Junk Mail" sign on my letter box, however I am constantly receiving advertising material both hand delivered and from the postal service. Being as there are 19 units here, the litter, waste and pollution is a constant blight at my front gate. If people want junk mail it can be picked up by the person. It is a great waste of resources which are generally just discarded. Does anyone else feel this way? I feel a petition is needed but would like some support. presently I am emailing the companies concerned and if they continue with the offence I put in a review on product review. In the past I have sent heavy letters stating my case to the offenders with no stamps in the hope that they will be liable for unpaid postage, however I'm not sure of the efficiency of this. All suggestions welcomed.