A union representing federal asylum officers said in a court filing Wednesday that the Trump administration’s policy forcing migrants to wait in Mexico while their asylum cases are decided risks violating international treaty obligations and “abandons our tradition of providing a safe haven to the persecuted.”

The union, which represents 2,500 Department of Homeland Security employees, including the asylum officers, said in its filing that the policy, the Migration Protection Protocols, puts migrants in danger because they could face persecution while being forced to wait in Mexico, undermining the purpose of asylum.

Citing a State Department report, the union said that “impunity for human rights abuses remained a problem” in Mexico. Migrants are at particular risk of being sexually assaulted, it said, and ethnic minorities could face “persecution similar to the persecution they face in their home countries.”

“Asylum officers are duty bound to protect vulnerable asylum seekers from persecution,” the union said. “They should not be forced to honor departmental directives that are fundamentally contrary to the moral fabric of our nation and our international and domestic legal obligations.”