The outcome of the Supreme Court’s order that the Biden administration restart former President Donald Trump’s “remain in Mexico” policy and begin sending asylum-seekers back to the other side of the border depends on whether Mexico will allow migrants to be returned.

The likelihood that the Migration Protection Protocols, as the program is known, will be carried out is thought to be low, given that Mexico has refused to accept back other migrants sent from the United States under a different U.S. policy.