President Donald Trump’s deputies may soon finalize a “safe third country” deal with Guatemala that would allow U.S. border officials to legally block most migrants from even applying for asylum, according to the New Yorker magazine.

The Guatemala deal would create a legal wall on the U.S. border that would prevent migrants from asking for asylum or getting released into the United States, according to the outlet:

According to a draft of the agreement, which The New Yorker has obtained, asylum seekers from any country who either show up at U.S. ports of entry or are apprehended while crossing between ports of entry could be sent to seek asylum in Guatemala instead … Under this new arrangement, most of these migrants will no longer have a chance to make an asylum claim in the U.S. at all. “We’re talking about something much bigger than what the term ‘safe third country’ implies,” someone with knowledge of the deal told me. “We’re talking about a kind of transfer agreement where the U.S. can send any asylum seekers, not just Central Americans, to Guatemala.”

Pro-migration advocates are appalled because they are concerned the agreement might effectively bar the catch and release of the many economic migrants who ask for asylum at the U.S. border.

“This is reaaallly big news,” said a tweet from Aaron Reichlin-Melnick, an advocate at the migration industry’s Immigration Council advocacy group. “It will be challenged in court but it’s likely an uphill battle.”

Pro-American reformers are hopeful, partly because the vast majority of worldwide migrants must pass through Guatemala to reach Mexico and then the U.S. border.

“It is significant,” said Jessica Vaughan, policy director at the Center for Immigration Studies. The legal deal would allow U.S. officials to quickly reject asylum claims by northbound migrants from Honduras and El Salvador — or from Africa, India, Asia, and South America — on the grounds that they had declined to apply for asylum in Guatemala.

The New Yorker reported:

The draft of the agreement doesn’t provide much clarity on how it will be implemented—another person with knowledge of the agreement said, “this reads like it was drafted by someone’s intern”—but it does offer an exemption for Guatemalan migrants, which might be why the government of Jimmy Morales, a U.S. ally, seems willing to sign on. Guatemala is currently in the midst of Presidential elections; next month, the country will hold a runoff between two candidates, and the current front-runner has been opposed to this type of deal. The Morales government, however, still has six months left in office.

The deal also helps Mexico because it would allow Mexico to easily repatriate migrants who refuse to apply for asylum as they pass through Guatemala.

The likely price for America, Vaughan said, is more aid to Guatemala and Mexico. However, the extra aid will be far cheaper than the cost to Americans’ wages, schools, and rents that would be imposed by arriving migrants.

American pro-migration lawyers will fight the deal, she predicted, but the deal will likely persuade migrants that the benefits of migration northwards is not worth the financial cost. That would be bad news for the cartels because the coyotes’ labor-trafficking business only works if the migrants can repay their debts with American wages, she said.

The deal “strikes a blow to the smuggler’s business model,” she said.