Natural Law and Immigration

I have recently been reading a book titled "Philosophy In The Mass Age" by George P. Grant. Chapter 3 is  listed as 'Natural Law'. The chapter causes me to think about how I might observe natural law in action, and based on that observation adhere to it for my benefit.

The first example I use is BEES. 
In 1851, the Reverend Lorenzo Lorraine Langstroth (1810–1895), a native of Philadelphia, noted that when his bees had less than 1 cm (3/8 inch) of space available in which to move around, they would neither build comb into that space nor cement it closed with propolis. This measurement is called "bee space". During the summer of 1851, Langstroth applied the concept to keeping the lid free on a top-bar hive, but in autumn of the same year, he realized that the "bee space" could be applied to a newly designed frame which would prevent the bees from attaching honeycomb to the inside of the hive box.
Ref: https://en.wikipedia.org/wiki/Langstroth_hive

Having unintentionally not adhered to this 'natural law' of bee space with the handling and layout to one hive I found the result to clearly demonstrate my error. What a mess.

Another example I use is about "Sacred Foods".

In this video: https://www.youtube.com/watch?v=7ixsBn_lfXE

Sally Fallon of Weston Price Foundation, the author of Nourishing Traditions Cookbook, gives a presentation that discusses the research work of dentist, Weston Price in the early part of the last century. There are compelling 'before and after' photos in this presentation that demonstrate just how our modern diet affects people in first and then second generation children. She presents an interesting case for how this diet affects our DNA expressing its fullest genetic potential, and gives plenty of slow food for thought about how we may be able to turn this degeneration of our genetic expression around by learning from our elders, so to speak... the traditions of the indigenous people that Weston Price researched...

My father came from a village in Latvia where it was customary to regularly eat liverwurst, herring and dairy products - these are all sacred foods (A, D & K - the activator vitamins). He had a beautiful bone structure and perfectly laid out teeth as was depicted in Sally Fallon's videos in those individuals who adhered to a diet including sacred foods.

Both these examples demonstrate that "adherence to a natural law" provides a significant benefit. Man did not make this law, but has the capacity to observe it and then obey it.

This shows to me that the universe is an ordered whole, (cosmos), is in a state of equilibrium, is designed.

How can we apply this principle of "adherence to a natural law" in regard to immigration?
Does natural law even have an answer? I believe it does.

In my home I am happy to have guests come and go, but I only live long term with people who share similar values. As a parent I attempt to train my children to hold similar values as I. In fact I make specific discriminatory choices for them in regard to custom, education, religion, work ethic, expected intellectual achievement. How my children turn out is partly due to this, also their own capacity, and also the community, political and religious environment they are exposed to.

I note this point of view is consistent with other cultures and races.

There is a preference for your own, a natural law.