U.S. President Donald Trump tweeted Sunday that people who enter the United States illegally should be deported with "no Judges or Court Cases."
The American Civil Liberties Union responded to Trump's tweets by saying the system he wants goes against the protections provided by the U.S. Constitution.
"What President Trump suggested here is both illegal and unconstitutional. Any official who has sworn an oath to uphold the Constitution and laws should disavow it unequivocally," the rights group said.
The United States for years has granted court hearings to migrants fleeing from Mexico and Central American countries, and from elsewhere in the world, and looking for better economic fortunes in the United States.
Trump's demand to end that legal process would face stiff opposition in Congress, which for years has been stalemated on changes to U.S. immigration policies and unable to enact new migration laws.
The Republican-controlled House of Representatives is planning to vote this week on comprehensive immigration policy changes, after last week defeating a tougher version of new immigration controls.
Also last week, Trump signed an executive order maintaining his "zero tolerance" policy of detaining and prosecuting everyone entering the country illegally, but ending the practice of separating immigrant parents and children.
Logistical questions about those being detained have sent multiple government agencies in search of solutions, including how to provide housing.
Defense Secretary Jim Mattis told reporters traveling with him on a trip to China that the Pentagon is working closely with the Department of Homeland Security to build temporary camps on two military bases. Mattis said he could not yet name them, but promised to provide those details Monday.
He said military personnel do not play any enforcement role that is carried out by DHS, but have experience in supporting refugees and victims of natural disasters.
"This is something that we can do, again whether it be refugee boat people from Vietnam, people who have been knocked out of their homes by a hurricane, absolutely it's appropriate the military provide logistics support however it's needed," Mattis said.
Trump's latest immigration comments came hours after the Department of Homeland Security said it knows the location of 2,053 children it is holding, who were separated from their parents in recent weeks as they entered the country illegally along its southern border with Mexico, and is now working to reunite the families.
The agency said late Saturday 522 children have been returned to their parents, with many of them held together in detention centers while they await court proceedings to consider their bids for asylum in the United States.
But how quickly the remaining reunifications might occur remains an open question. A processing center in the southwestern state of Texas has been set up for the reunifications, which could lead to the deportation of some of the families.