The Trump administration will no longer allow migrant families apprehended at the border to enter the U.S. under the immigration policy commonly known as "catch and release."

The policy change was announced Monday by Acting Secretary of Homeland Security Kevin McAleenan in remarks at the Council on Foreign Relations in Washington, D.C.

"With some humanitarian and medical exceptions, DHS will no longer be releasing family units from Border Patrol Stations into the interior," McAleenan said in his prepared remarks. "This means that for family units, the largest demographic by volume arriving at the border this year, the court-mandated practice of catch and release due to the inability of DHS to complete immigration proceedings with families detained together in custody — will have been mitigated."

In a statement issued by DHS, the agency outlined how it intends to carry out its new policy starting next week.

"If migrant family units do not claim fear of return, they will be quickly returned to their country of origin, in close collaboration with Central American countries," the statement read. "If they do claim fear, they will generally be returned to Mexico under the Migrant Protection Protocols (MPP)."

Under the MPP, the U.S. government sends asylum-seeking migrants to Mexico, where they reside as they wait for court dates in the U.S. to pursue their claims for protection. The program, also known as "Remain in Mexico," has come under widespread criticism for failing to protect migrants with legitimate fears of returning to their homeland.

McAleenan said the end of "catch and release" is a reaction, in part, to the record number of 144,000 migrants apprehended or encountered at the southern border in May. He said that 72% were unaccompanied children or families.

The announcement follows an agreement signed last week by El Salvador and the U.S. in which the Central American nation agreed to allow some asylum-seekers to request protection there rather than the U.S. The operational details of that deal were not disclosed.

Earlier this month, the U.S. Supreme Court, by a vote of 7-2, allowed the administration to implement a rule requiring migrants to first seek asylum in "a third country." In other words, the country through which they traveled to get to the United States.

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