A Republic — Rule of Law. Illegal immigration would be punished as a crime, and security would be pursued.
A democracy — Rule by the People. If the majority of the people want border security, then border security should be pursued.
An Oligarchy — Powerful people do whatever they want.
We have the illusion of self rule. That is what the Roman Emperors did too, they bought off the Senate and made it look like the people had a say in government but it was an illusion. A placation. Bread and circuses.