As the Trump administration ships migrants to countries around the world, it is abandoning a longstanding U.S. policy of not sending people to places where they would be at risk of torture and other persecution.

The principle emerged in international human rights law after World War II and is also embedded in U.S. domestic law. It is called “non-refoulement,” derived from a French word for return.

The issue came into sharp relief in the past month as the Trump administration has tried to deport migrants with criminal records to Libya and South Sudan, countries considered so dangerous that they are on the State Department’s “do not travel” list.

“What the U.S. is doing runs afoul of the bedrock prohibition in U.S. and international law of non-refoulement,” said Robert K. Goldman, the faculty director of the War Crimes Research Office at American University’s law school.

In a recent affidavit, Secretary of State Marco Rubio described the Trump administration’s efforts to send migrants to those two countries as part of a diplomatic push to improve relations. He acknowledged that the Libyan capital, Tripoli, was wracked by violence and instability.

To critics of the administration, the sworn statement shows that the United States is no longer considering whether a deportee is more likely than not to be at risk of abuse through repatriation or transfer to a third country.