Borders are there to protect societies from dangers, lawbreakers, potential lawbreakers. etc... they are not there to prevent the innocent from coming in.
If an innocent person jumps through your fence to escape a robbery, dangers, etc would you accept him/her or not? Ofcourse, you will, unless you are unnecessarily a hardened person. But you will need to be sure he/she is telling the truth. And you'll need to shelter that person until he/she feels safe to leave.
One the reasons I am bringing this up is to be able to deal with the issue easily in decentralized world. Decentralization, permissionless and trustlessness will need to be maintained with little to no risk to communities. Besides, we are heading to a point where people will see the need for both open and close border. And those who fail to do things the proper way during that time will be in trouble.
problem is economic, those in the society created a structure, of exploitation, they start wars against other structures, in order to get soil for themselves the soil is desperate hard working labour.
muslims for example don't think in borders they think in belief systems which is in my oppinion not a bad idea. but it has also sideeffects regarding oppenness.
regards