It sounds like a good idea and I have considered it myself for a while. It may not seem like a great idea to have an immigration and importation process and con

It sounds like a good idea and I have considered it myself for a while. It may not seem like a great idea to have an immigration and importation process and controls at first. However, consider the realities that are encountered. A few examples: Years ago, the European pioneers showed up 'freely' and for all intents destroyed the Native Americans' way of living (and many of their lives). There have been areas with diseases in humans and animals in certain countries that are much less common in others, that could cause disastrous scenarios for livestock, agriculture, and humans if introduced haphazardly. People also showed up 'freely' and kidnapped humans from Africa and sold them as slaves in the US. If one argues that there should be rules in place to prevent such things from happening, then you essentially need a process by which to discriminate whether 'outsiders', and how many, should be allowed in one's physical space (edit: along with sufficient military force to repel a large group that will attempt to forcefully ignore such a process).