I'm just stating there are numerous plants and animals that are not indigenous to the United States, or wherever for that matter, that can cause widespread damage. There has to be some form of control. If unidentified seeds or plants are just stuffed into an envelope, with no labeling or corresponding paperwork, what is Customs supposed to do, just let everything through? I think not. Kudzu was merely an example of a plant that got out of control, and does to this day, not unlike the mitten crab in the Thames, Zebra mussles in fresh water areas in the US, etc.