The Supreme Court has temporarily blocked a lower court ruling that struck down the president’s ban on ghost guns.It was last year the president announced his crackdown on ghost guns—those sold as do-it-yourself kits and that are generally hard to trace. A federal judge in Texas had ruled with gun rights groups that achieving the ban by changing the definition of  a gun exceeded the ATF’s authority.  The Supreme Court’s emergency ruling pauses that decision as the case moves to an appeals court next week.