Whenever you find a libertarian defending immigration controls, you will see one distinguishing characteristic of his defense: the absence of any discussion about immigration enforcement measures. There is a simple reason for that. Immigration enforcement measures entail the initiation of force against others and, therefore, violate the fundamental principle of libertarianism, commonly known as the non-aggression principle. Since libertarians who support immigration controls do not wish to appear to be advocating a violation of the core principle of libertarianism, they always talk in terms of supporting immigration controls while, at the same time, remaining silent about how the government enforces such controls.

Obviously, simply by enacting a law prohibiting foreigners from entering the United States without official permission would be insufficient to accomplish the aim of the law. That’s because most foreigners who want to come to the United States would simply ignore the law and enter the country anyway.

That’s where the enforcement mechanisms come into play, enforcement mechanisms that not only violate the libertarian non-aggression principle but also inevitably move a nation toward an immigration police state.

Consider the highway checkpoints in the American Southwest. The border agents at those checkpoints stop people who are travelling domestically and who might never have entered Mexico. After being forced to stop, if the traveler refuses to lower his window and answer questions or permit his vehicle to be searched, government agents smash in his window, drag him from his car, and sometimes even beat him up. They will also conduct a full-scale search of his vehicle, without a warrant. If they find drugs, they’ll charge him with possession. That’s a clear-cut case of initiating force. It shouldn’t surprise anyone that these types of highway checkpoints are found in countries that are run by totalitarian or authoritarian regimes.

How can any libertarian who wishes to adhere to libertarian principles support such a measure knowing that it violates the core principle of libertarianism?

Or consider what the federal government is doing to the National Butterfly Center, a private facility located in Mission, Texas. According to an article in Monday’s New York Times, last month Marianna Wright, the center’s executive director, discovered a work crew cutting down trees and brush on the center’s property. The crew had been employed by U.S. Customs and Border Protection to begin preparing to build Trump’s Wall along the Southern border. No warrant. No court order. Just trespass — i.e., the initiation of force by government agents against a private landowner. After Wright objected and threw the crew off the center’s private property, the Border Patrol’s sector chief for the Rio Grande Valley, told her that the men would return later with a team of armed Border Patrol agents. The implication was clear: interfere and we will arrest you or, if you violently resist, shoot you. It would be difficult to find a better example of the initiation of force than that. And it’s going to happen to privately owned landowners up and down the Rio Grande and the rest of the U.S.-Mexico border to build a wall that will inevitably resemble the Berlin Wall.

How can any libertarian who wishes to adhere to libertarian principles support such a measure knowing that it violates the core principle of libertarianism?

Of course, the construction of Trump’s Wall won’t stop with government trespass onto private property. The government will also initiate eminent domain proceedings to forcibly take away a portion of the people’s land where the wall will be constructed. That’s legalized stealing, even if the government is required to pay fair market value for the land it is stealing.

How can any libertarian who wishes to adhere to libertarian principles support such a measure knowing that it violates the core principle of libertarianism?

In the Southwest, U.S. Border Patrol agents regularly enter onto privately owned ranches and farms. This happens not just for properties located adjacent to the border but also for properties located several miles away from the border. No warrant or any other court order. Just plain old trespass onto people’s privately owned property. What happens if a ranch farm owner says no? They pull out their guns and arrest them. Obviously, that constitutes initiation of force.

How can any libertarian who wishes to adhere to libertarian principles support such a measure knowing that it violates the core principle of libertarianism?

Throughout the nation, armed immigration agents regularly enter into private businesses and arrest foreigners who are working pursuant to a consensual agreement of employer and employee. What happens if employers or immigrants resist the arrest? The immigration agents arrest them, charge them with obstruction of justice, and cart them off to prison. That’s initiation of force against people who are exercising liberty of contract and engaging in purely peaceful, productive activity.

How can any libertarian who wishes to adhere to libertarian principles support such a measure knowing that it violates the core principle of libertarianism?

Of course, a libertarian who supports immigration controls can say, “Jacob, I support immigration controls but not those specific enforcement measures because I know they entail a violation of the libertarian non-aggression principle.”

Okay, so here is my challenge to libertarians who support immigration controls: List and detail the enforcement measures that you favor and that you believe will finally, once and for all, bring an end to the decades-long immigration crisis that immigration controls have produced. Show us why you think they will succeed while all the government’s enforcement measures have failed. Finally, show us how the enforcement measures you favor do not violate the libertarian non-aggression principle. You can’t do it.