Worldwide refugee law says that asylum seekers have the right to lodge asylum claims irrespective of illegal entry or presence, which U.S. asylum law affirms by saying, "any alien who is physically present in the United States or who arrives in the United States (whether or not at a designated port of arrival...) irrespective of such aliens status, may apply for asylum".
Thousands of people from Guatemala, Honduras and El Salvador have fled poverty and violence in their homelands and made their way to the United States.
The change to asylum procedures was published Thursday by the Justice Department. "It is illegal to circumvent that by agency or presidential decree", he said.
Immigration was a major focus in President Trump's 2018 mid-term election campaign.
The rule, which prevents migrants from claiming asylum if they do not do so at an official border crossing, is the latest attempt by the White House to handle a surge in migration to the USA from the Central American countries of Guatemala, Honduras and El Salvador.
The joint statement said presidents have the power to "suspend the entry of all aliens" and to impose "any restrictions he may deem to be appropriate on them" if they are judged to be "detrimental" to USA interests under the Immigration and Nationality Act.
"Although the Trump administration expects to be enjoined and stopped in the near term", one of the officials told NBC, "they believe a policy based on the discretionary authority of the president over who is admitted to the USA will ultimately hold up in the Supreme Court".
"Today, we are using the authority granted to us by Congress to bar aliens who violate a Presidential suspension of entry or other restriction from asylum eligibility", they explained.
The regulations will be incorporated in a proclamation expected to be issued Friday by President Donald Trump.
Trump said he was sending 15,000 active duty military to the border to deal with the problem, in what former President Barack Obama called a political 'stunt.' The troops began laying barbed wire as the migrants traveled toward the US on foot.
The American Civil Liberties Union swiftly declared the move "illegal".
Immigrant advocacy groups have complained that under Trump, U.S. border police have made it more hard for people to cross into the country at ports of entry and have outright turned away some migrants.
"President Trump's Proclamation is yet another attempt to destroy the United States´ long tradition to guarantee the fundamental human right to seek protection from life-threatening fear and persecution". Under global law, these are considered refugees.
On a call with reporters Thursday, senior administration officials emphasized that point, claiming that it would mean asylum claims will be handled more efficiently.
"The narrative that people seeking refuge are a security threat is a manufactured crisis by the Trump administration rooted in the politics of hate and fear".