While the Supreme Court has agreed to review the constitutionality and legality of the third travel ban, the Fourth Circuit has joined the Ninth Circuit in striking it down. The Fourth Circuit concluded it likely violates the Establishment Clause because its primary purpose is to discriminate against Muslims.
Per a December 2017 Supreme Court order, the third travel ban is currently in effect regardless of the Ninth and Fourth Circuit rulings.
On September 24, 2017, President Trump issued a presidential proclamation (the third travel ban) indefinitely banning immigration from six countries: Chad, Iran, Libya, North Korea, Syria, and Yemen. Lawsuits were brought immediately in the Ninth and Fourth Circuits.