Supreme Court will decide where asylum protections begin at the border

• The Supreme Court case comes after the 9th Circuit Court of Appeals ruled that a policy of turning away asylum seekers before they could physically set foot on American soil to begin the application was illegal.

Zoom out: Under U.S. law, any person "physically present" in the U.S. or who arrives at the border must be given an opportunity to seek asylum, according to the American Immigration Council.

• Since 2016, though, U.S. Customs and Border Protection has turned people away via a process called "metering."
• "Under metering, CBP officers assert a lack of capacity to refuse to inspect and process asylum seekers, requiring them to wait for weeks or months in Mexico just for the opportunity to start the asylum process," per the Council.

What they're saying: "The government's turnback policy was an illegal scheme to circumvent these requirements by physically blocking asylum seekers arriving at ports of entry and preventing them from crossing the border to seek protection," attorneys for the asylum seekers wrote on Monday.

• "As our attorneys have already made abundantly clear, the Trump administration has advanced the clear meaning of federal law and basic common sense in this case since day one," Homeland Security spokesperson Tricia McLaughlin said. "We look forward to presenting our case to the Supreme Court."

Context: A dissenting 9th Circuit judge concluded that a migrant "arrives in the United States" only upon crossing the border, per Justia.

Go deeper: U.S. Catholic bishops call for end to "dehumanizing rhetoric" on immigrants

Editor's note: This story has been updated with comment from the Department of Homeland Security.