The "Remain in Mexico" immigration policy is coming to an end, more than three years after it was first implemented by the Trump administration.
Aaron Reichlin-Melnick is the Policy Director at American Immigration Council.
"This decision is an unqualified victory for the Biden administration," Reichlin-Melnick said.
Lower courts had previously blocked President Biden from ending the policy, which forces thousands of asylum-seekers to wait in Mexico while their cases play out.
On Thursday, the Supreme Court gave the Biden White House permission to wind down the program, reasoning that the President should decide how to implement his own foreign and immigration policy.
Critics have long called the "Remain in Mexico" policy inhumane and ultimately ineffective.
They say it exposes migrants with valid claims to squalid conditions, sexual assault and kidnapping and makes it hard to obtain an attorney.
"This year, I've interviewed hundreds and hundreds of families. All of them have been kidnapped, raped, attacked at gun point. At least once, if not two or three times. It's insane,"said Jennifer Harbury, a human rights lawyer.
Texas and Missouri had sued the Biden administration to keep the program in place amid a record level of unauthorized border crossings.
Still, there's another and more restrictive Trump-era immigration policy that's still in use despite White House efforts to repeal it: Title 42.
That one empowers U.S. Border agents to swiftly expel most migrants without screening their asylum claims.
It was put in place in the early days of the pandemic to limit virus spread.
The Biden administration tried to end that public health policy in May, but a federal judge kept it alive after Republican states sued.
"Title 42 is going to remain in effect for the foreseeable future. And that means thousands more people are going to be expelled back to Mexico. The ports of entry are going to remain closed to asylum seekers. And the chaos and confusion and arbitrary patchwork of outcomes created by Title 42 will continue even after this decision," Reichlin-Melnick said.
For migrants fleeing violence and poverty, keeping up with these ever-changing border policies is nearly impossible.
"The reality is, we don't have a system at the border. We have a set of policies which apply to different people differently depending on the day. That's not a good way to run the border," Reichlin-Melnick said.
Advocates say when the door to asylum is closed, people are more likely to seek dangerous ways to sneak across often with the help of unscrupulous smugglers.
In San Antonio, on Monday, it all turned tragic.
In what may have been the nation's deadliest smuggling incident, more than 50 Mexican and Central American migrants were found dead inside a truck in the sweltering Texas heat.
