An immigration hawk says now is the time to finally “cut off” the “magnet” that brings most illegal aliens to the United States–job opportunities.

In a Hill piece by Robert Law, a fellow with the Federation for American Immigration Reform (FAIR), the expert says that while much focus has been put on President Trump’s proposed–but yet to be built–border wall, equal attention should be placed on ending U.S. employers from being allowed to hire illegal aliens:

President Trump’s signature campaign pledge was to build a “big, beautiful wall” along the U.S.-Mexico border to stop the flow of unlawful border crossings. Crowds of Trump supporters at rallies across the country memorably shouted in unison, “Build the Wall!” over and over again. While the president’s tough rhetoric on illegal immigration has already dramatically reduced the flow of unlawful border crossings, constructing a physical barrier — whether you call it a wall, fence, or something else — is necessary to prevent the flood gates of illegal immigration from reopening under a different administration. But the illegal immigration issue is more complex than sealing the southern border. First, the U.S. has at least 11 million illegal aliens already living inside the country. Additionally, around 40 percent of the illegal alien population are visa overstays—those who entered the U.S. legally for a limited period of time and simply refuse to go home. The border wall won’t address these aspects of illegal immigration. To truly combat illegal immigration you must eliminate the pull factors, with the ability to work unlawfully in the country without fear of repercussions being the most significant magnet. To borrow an old Bill Clinton campaign slogan: it’s the economy stupid. That’s why we need mandatory and universal E-Verify.

Under E-Verify, U.S. employers are able to electronically verify within seconds whether or not potential employees are legally in the country. Law writes that although it is currently difficult for employers to verify eligibility without E-Verify, he says some employers skirt federal law.

“Too often, unscrupulous employers intentionally look the other way because illegal aliens work for below market wages that pad businesses profit margins,” Law writes. “These employers should face heavy fines as part of mandatory E-Verify reform.”

In a recent study of states which already mandate employers use E-Verify, as Breitbart News reported, found that all but one of the states saw their unemployment rates drop, despite the national rate actually increasing at the same time. In addition, 12 of the 15 states that passed new legislation “experienced a drop in unemployment larger than the national average.”

The FAIR study also found that all states which mandate E-Verify for employers saw the “most profound” decrease in unemployment rates.

“E-Verify will end the lure of jobs that entices visitors to overstay their visas in the first place, while also dissuading those who might still try to illegally cross our borders for work,” Law continued. “The most effective and humane way of enforcing laws is to convince people there is no benefit in breaking them. When we finally shut off the magnet that draws workers here, we’ll also shut off much of the flow, while protecting the jobs and wages of our most vulnerable workers.”

Senator Chuck Grassley (R-IA) introduced the Accountability Through Electronic Verification Act, which would mandate E-Verify for all U.S. employers. Grassley’s legislation has yet to go before the Judiciary Committee, for which he is the chairman.

John Binder is a reporter for Breitbart Texas. Follow him on Twitter at @JxhnBinder.