SAN ANTONIO — The Trump administration may not be able to move mountains — literally — in its quest to build a coast-to-coast wall along the nation's southern border.  

But that doesn’t mean the White House won’t review some long-standing treaties that have stymied past administrations in their efforts to erect such barriers, a former acting commissioner of Customs and Border Protection said Tuesday. 

“I think a lot of the different treaties and regulations, other federal laws, are all going to be reviewed as part of this process because they have been impediments in the past,” said Jayson Ahern, who spent 33 years with the federal government, including a five-year term as assistant commissioner for CBP's field operations from 2002 to 2007. 

Ahern spoke to The Texas Tribune during a border security expo in San Antonio, where officials also predicted the Trump administration could expand the number of employers required to use E-Verify, a federal electronic employment verification system that screens for unauthorized workers.

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When it comes to blocking the border, an existing treaty between the United States and Mexico says any structure built near the Rio Grande cannot disrupt the river's natural flow. Another regulates how the two countries manage shared surface water. Both treaties could hinder the construction of a barrier near the river. The treaties can be changed, but it would require the sign-off of both nations. 

Ahern said every new president quickly learns that existing policies can complicate campaign promises. Environmental regulations and treaty issues were factors former president George W. Bush had to contend with after he signed 2006's Secure Fence Act, which resulted in the construction of about 650 miles of border fence. 

Ahern said Trump is likely to do as much as possible to fulfill his promises.

“I think the administration is ... realizing some of the challenges that are out there that have actually been realized by others,” he said. “And I think that’s good."

Though the wall and Trump’s early emphasis on U.S. immigration enforcement have garnered most of the country’s attention, another former high-ranking official said Congress could consider an E-Verify bill for all the nation's employers as early as next year.

“They’ve brought up a lot of proposals over the years, and I think now, with Republicans leading both the House and the Senate and the administration, they see this as an opportunity to bring forth some of the ideas and actually enact them,” said Kate Mills, who served under President Obama as the assistant director for Immigration and Customs Enforcement's Office of Congressional Relations.

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The E-Verify system, which is operated by U.S. Citizenship and Immigration Services, screens for undocumented workers by comparing the information that job applicants submit to an employer with records maintained by the Department of Homeland Security and the Social Security Administration. It’s only mandatory nationwide for federal contractors, although states may craft their own E-Verify policies.

Texas’s current policy mandates E-Verify only for state agencies and the companies they contract with. Some lawmakers say it doesn’t go far enough because the majority of private companies that hire unauthorized workers don’t use the system.

Mills said federal lawmakers are currently looking into how to make the program easier to use and how to take some of the burden off of employers who aren’t immigration experts.

“[They] are looking at ways that they can make the process a little more streamlined to make the information more accurate,” she said.  

Read more related coverage: 

  • At the U.S.-Mexico border, scientists say existing fencing is hurting endangered wildlife and warn that a continuous wall could devastate many species. 
  • None of the 38 Texans in Congress offered a full-throated endorsement of a complete border wall, a position popular with President-elect Donald Trump's supporters, a Texas Tribune delegation-wide survey in December found.
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