"In its 6-to-3 ruling, the court said noncitizens must fully cross the border to gain the right to apply for asylum. The court’s conservative majority said migrants standing in Mexico do not 'arrive' by 'attempting, and failing, to set foot in this country.'"

From "Supreme Court Allows Trump to Block Asylum Seekers at Border/A policy of turning back asylum seekers at the border was rescinded in 2021, but the Trump administration wants the flexibility to reinstate it as a tool for border control" (NYT).

Here's the full opinion: Mullin v. El Otro Lado. Excerpt from the majority opinion, written by Justice Alito:

This case presents a straightforward question: whether an alien1 who seeks to enter the United States from Mexico “arrives in the United States” when he or she is still in Mexico. In the decision below, the United States Court of Appeals for the Ninth Circuit answered “yes.” That is wrong. In ordinary speech, no one would say that a person “arrives in” a place—for example, a house, a city, or a country—before the person enters that place. The context in which the phrase “arrives in the United States” is used in the immigration statutes at issue here supports an ordinary-meaning reading. So does the presumption against extraterritoriality. We therefore reverse.

 From Justice Sotomayor's dissenting opinion (joined by Justices Kagan and Jackson):

The Court’s illogical interpretation is driven almost entirely by a fixation on a single word: “in.” Words, however, must be read in context and with attention to how they fit into the statute as a whole. The majority ignores the statutory context and history, not to mention the longstanding position of the Executive Branch, all of which show that any noncitizen arriving at our doorstep and seeking admission must be inspected and allowed to apply for asylum, regardless of whether her foot has crossed the threshold....