The Ninth Circuit’s decision against President Trump’s immigration order is worse than wrong. It is dangerous. To review, Trump issued an executive order blocking entry by refugees and aliens from seven Muslim-majority countries. The travel restriction is to be short-lived: a period of months while better vetting procedures are developed. The administration, moreover, did not pluck the seven countries from its allegedly anti-Muslim imagination. They were cited in a statute enacted by Congress and signed by President Obama, based on the richly supported conclusion that these countries — Iran, Iraq, Syria, Yemen, Libya, Somalia, and Sudan — are riven by...