As President Trump is discovering, there are a lot of very difficult, complicated issues he has to deal with. Healthcare, Syria, North Korea and the Russians are a few that come to mind. Controlling our borders and stanching the flow of illegal aliens into the United States, it turns out, is not one of them. In fact, in just the first three months of his administration, dealing with mass illegal immigration is proving to be one of the least complicated matters on the president's plate.

For decades, apologists for mass illegal immigration have been telling us that a) illegal immigration isn't really a problem, and b) that it an uncontrollable phenomenon in any event. Attempting to stop mass illegal immigration would be an expensive and futile effort.

It turns out that the so-called experts were wrong. In just the second full month of the Trump presidency, the number of people apprehended attempting to enter the United States illegally plummeted to 17-year lows. Moreover, the "surge" of illegal migration from Central America of unaccompanied minors (UAMs) and families with children suddenly stopped surging. As recently as December (not coincidentally, the last full month of the Obama presidency), more than 7,000 UAMs arrived at our southern border. By March, that number had dwindled to just 1,914. Likewise, the flood of 16,139 people arriving in family units in December was reduced to a trickle – just 1,043 people in March – a decline of 93 percent.

Even more remarkably, these dramatic declines in the number of people attempting to cross our border transpired before the first dime has been expended on construction of Trump's "big beautiful wall," and before the first of the administration's requested 5,000 new Border Patrol agents was hired, much less trained and deployed to the front lines.

Illegal immigration has always been a manageable problem. Illegal immigrants are rational people who respond rationally to the signals we send. When our policies convey the sense that we are not serious about enforcing our immigration laws (which has largely been the case for decades), they behave accordingly. Just the mere indication on the part of the Trump administration that they intend to enforce our laws has been sufficient to discourage many people from even attempting to come here illegally.

The president has also taken concrete actions to demonstrate that he is serious about deterring illegal immigration. Among other steps, he has ended the catch-and-release policy of the Obama administration, under which people arriving at the border were permitted to enter the country pending a hearing, often years in the future. The Trump administration, while continuing to prioritize the removal of criminal aliens, has made it clear that it will not exempt all other immigration lawbreakers from deportation.

Now it is up to Congress to reinforce these positive results with long overdue legislative reforms. In addition to funding the president's security barrier (which Congress authorized in 2007) and additional enforcement personnel, lawmakers must address the key pull factors of illegal immigration, most notably the availability of jobs to illegal aliens.

More than three decades after Congress outlawed the employment of illegal aliens, it is time to put teeth in that law. E-Verify, which allows employers to instantly check job applicants' information against Social Security and other government databases, must be made a mandatory part of the hiring process. As illegal aliens come to understand that they will no longer be able to use fraudulent or stolen documents to skirt the law, and employers understand that they will be held accountable if they are caught hiring illegal aliens, the lure of a job in this country will be greatly diminished.

Ironically, discouraging economic migrants from entering and remaining in the country illegally would vastly enhance our ability to target criminal aliens for removal. By eliminating the chaos that has long existed at our borders, fiscal and manpower resources can be devoted to identifying, apprehending and removing aliens who cannot be discouraged by diminished prospects of employment or access to public benefits.

The first few months of the Trump administration have shown that decades of mass illegal immigration were not a consequence of forces beyond our control, but rather the predictable result of politically driven policy choices we have been making. The biggest factor in managing illegal immigration is managing the perceptions of those who are weighing the pros and cons of breaking our laws – which is actually not that complicated.

Ira Mehlman is the media director of the Federation for American Immigration Reform (FAIR).

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