Confronted with a surge of migrants, the Biden administration has decided to waive more than 20 federal laws, including environmental ones, to erect barriers along the Southern border.

The decision represents a significant reversal for President Biden, who campaigned vociferously against a wall along the U.S.-Mexico border, which his predecessor had championed as a key deterrent to unlawful crossings.

Alejandro Mayorkas, the homeland security secretary, said that easing the laws was necessary to expedite construction of sections of a border wall in South Texas, where millions of migrants have been crossing the Rio Grande to reach U.S. soil.

A notice published in the Federal Register on Thursday said that the secretary, “has determined, pursuant to law, that it is necessary to waive certain laws, regulations, and other legal requirements in order to ensure the expeditious construction of barriers and roads in the vicinity of the international land border in Starr County, Texas.”

The U.S. Border Patrol in the Rio Grande Valley had encountered more than 245,000 migrants who had entered the country between ports of entry, or unlawfully, in the 2023 fiscal year that ended Sept. 30, the notice said.

“There is presently an acute and immediate need to construct physical barriers and roads in the vicinity of the border of the United States in order to prevent unlawful entries into the United States,” said Mr. Mayorkas in the official notice.