Customs and Border Protection Commissioner Kevin McAleenan (C) announced that the Trump administration will temporarily reassign several hundred border inspectors during a news conference at the border in El Paso, Texas, March 27, 2019.
Customs and Border Protection Commissioner Kevin McAleenan (C) announced that the Trump administration will temporarily reassign several hundred border inspectors during a news conference at the border in El Paso, Texas, March 27, 2019.

Victoria Macchi contributed to this report.

U.S. President Donald Trump announced Sunday his intention to appoint U.S. Customs and Border Protection (CBP) Commissioner Kevin McAleenan as acting Department of Homeland Security secretary, replacing current head Kirstjen Nielsen, who said she plans to leave the job Wednesday.

Trump's announcement on Twitter ends Nielsen's tenure of more than a year with the agency that oversees border security in the United States. Nielsen reportedly resigned, though some reports have said she was forced to leave.

McAleenan's appointment comes amid the administration's allegations of a surge of migrants at the U.S.-Mexico border.

지난 4일 미국 캘리í
FILE - Homeland Security Secretary Kirstjen Nielsen, center, and commissioner for Customs and Border Patrol Kevin McAleenan, left, walk with U.S. President Donald Trump during a visit to a section of the border wall in Calexico California, April 5, 2019.

McAleenan is not new to "acting" positions. He was acting commissioner of the CBP in January 2017 and was formally sworn in 2018. According to a CBP profile of him, the commissioner oversees a $16 billion budget in an agency with 60,000 employees — the largest law enforcement agency in the U.S. 

"We just hope that Nielsen's departure doesn't allow for new leadership to be put in place doubling down on policies to turn away vulnerable women and children. … We cannot effectively employ a law enforcement answer to what is a humanitarian problem," Krish O'Mara Vignarajah, president and CEO of Baltimore-based Lutheran Immigration and Refugee Service (LIRS), told VOA.

"Even if there is a shift to an extreme, I fear that we're going to come to a crashing collision, because we have to figure out a way to meet the letter of the law and meet the needs of families and children," Vignarajah said, adding that she appreciates in recent interviews that McAleenan has recognized the nature of border crossings, which has recently changed from single males trying to evade detection to families seeking asylum.

FILE - Photo provided by U.S. Immigration and Customs Enforcement shows mothers and their children standing in line at South Texas Family Residential Center in Dilley, Texas, Aug. 9, 2018.
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In recent weeks, McAleenan told reporters the U.S. immigration enforcement system along the nation's southern boundary was at "the breaking point," adding that CBP did not have the infrastructure to deal with families and children.

In December, he told the Senate Judiciary Committee that "our infrastructure is incompatible with this reality. Our border patrol stations and ports of entry were built to handle mostly male, single adults in custody, not families or children." 

McAleenan also blamed smugglers for the increase in illegal crossings and called the situation a "border security and humanitarian crisis," though historically, the number of illegal crossings between ports of entries are at an all-time low.

In fiscal year 2018, illegal crossing apprehensions at the southwest border — people detained between ports of entry only — totaled 396,579. In FY 2008, the number was 705,005. 

In FY 2016, apprehensions were at 408,870, while in FY 2017, the total was 303,916.

'Zero tolerance' policy

As CBP commissioner, McAleenan, under Nielsen's leadership, moved the Trump administration's "zero tolerance" policy forward — detaining and prosecuting everyone entering the country illegally, which resulted in the separation of minor children from their parents. 

Immigrant families walk along a sidewalk on their way to a respite center after they were processed and released by U.S. Customs and Border Protection, Sunday, June 24, 2018, in McAllen, Texas.
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The consequences of zero tolerance still remain.

In court documents filed Friday, the U.S. government said it might take federal officials two years to find "potentially" thousands of children who were separated from their families at the border before a judge halted the practice last year.

FILE - Immigrant children walk in a line outside the Homestead Temporary Shelter for Unaccompanied Children, a former Job Corps site that now houses them in Homestead, Fla., June 20, 2018.
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In an interview with New York Times Magazine, McAleenan said CBP is a "law enforcement organization carrying out policy and law set by others." He added that "there was no intent for indefinite and certainly not permanent separation. There's an intent to enforce the law at the border. And that's not an individual agent's decision. That comes from the top of the administration."

Trump's authority

Trump's McAleenan announcement came shortly after Nielsen's meeting with the president, but legal experts have questioned whether Trump has the authority to appoint McAleenan.

The issue, Stanford law professor Anne Joseph O'Connell tweets, is a statute guiding the Department of Homeland Security.

According to the statue, in case there is a need for an acting secretary due to a secretary of homeland security vacancy, the undersecretary for management is expected to become the acting secretary — which means the job would go to Claire Grady. 

In the past, Trump appointed Mick Mulvaney, his current acting chief of staff, as acting director of the Consumer Financial Protection Bureau, bypassing Richard Cordray's deputy. After Jeff Sessions was fired as attorney general, the president appointed Matthew Whitaker acting attorney general, going over higher ranking officials such as Rod Rosenstein.

McAleenan has a law degree from the University of Chicago. He practiced law in California before working for the U.S. government.

On Monday afternoon, Nielsen's farewell message was on the front page of the DHS website.