President Donald Trump says people who enter the United States illegally should be sent back immediately to where they came from without any judicial process, likening them to invaders who are trying to "break into" the country.
"We cannot allow all of these people to invade our Country. When somebody comes in, we must immediately, with no Judges or Court Cases, bring them back from where they came," Trump said on Sunday on Twitter.
"Cannot accept all of the people trying to break into our Country. Strong Borders, No Crime!"
It was unclear if Trump was advocating an expansion of the current law that allows expedited removal of illegal immigrants at the US border, a policy his administration has embraced since he took office. Nor did Trump differentiate between illegal immigrants and people who entered the US to seek asylum protection.
Critics say his proposal would violate the US Constitution's due process provision, which the Supreme Court has ruled also applies to non-citizens.
"The president of the United States has just forcefully proposed the end of political asylum and no due process for migrants," Sherrilyn Ifill, president of the NAACP Legal Defence Fund, wrote on Twitter.
Lee Gelernt, the deputy director of the ACLU's Immigrants' Rights Project, told Reuters: "The administration cannot simply get rid of all process for immigrants. The due process clause absolutely applies. It's not a choice."
US law does permit expedited deportations if an immigrant is apprehended within 100 miles (160km) of the border and has been in the country for less than 14 days. Those seeking asylum must be granted a hearing.
Trump's tweets on Sunday came after a week of global outcry over images and video of crying children and their distraught parents separated at the US-Mexico border. Critics in Trump's Republican Party, as well as his wife and daughter, urged him to abandon the policy.
Trump buckled to the pressure on Wednesday, issuing an executive order that ended the separations but the government has yet to reunite more than 2000 children with their parents.
However, the president's frustration over the issue only grew. He has issued a steady drumbeat of criticism of the immigration system and Democrats in ccongress, while using increasingly harsh terms such as "invasion" and "infestation" to describe illegal immigration.
Trump's "zero tolerance" policy of prosecuting adults for entering the country illegally entails a process that typically takes many months. That required children to be separated from parents because they are not legally allowed to be kept in detention for more than 20 days.
However, keeping the children with their migrant parents as they await court proceedings faces obstacles including lack of sufficient housing, a paucity of immigration judges and a daunting backlog of cases.
Under expedited removal proceedings, which are used most commonly at ports of entry, an immigration official can evaluate an immigrant's claim and reject it with no involvement by an immigration judge or review board.