A capitalist country secures its borders just like an individual secures their property: borders are closed to rights violating individuals, and open to rights-respecting individuals.

The difference between a country that secures its borders and an individual that secures their home is that under capitalism a private individual can close or open their home/business to whomever they wish, whereas the government is only permitted to close off migration to rights violating individuals.

What degree of security that is implemented depends on the context, i.e., one’s neighbors and neighborhood.