Texas v. Biden, a case with profound implications for American foreign policy, reached the Supreme Court with lightning speed. On August 13, a judge in Texas appointed by then-President Donald Trump effectively ordered the Biden administration to permanently reinstate Trump’s “Remain in Mexico” policy. That policy, which is officially known as the Migrant Protection Protocols (MPP), requires many immigrants who seek asylum in the United States to stay in Mexico while they await a hearing. Judge Matthew Kacsmaryk’s opinion in Texas was wrong for many reasons, including that he completely misread federal immigration law. Kacsmaryk wrote that a 1996 federal...