WASHINGTON—U.S. Chief Justice John Roberts on March 26, rejected a bid by gun rights activists to put on hold a ban by President Donald Trump’s administration on “bump stock” gun attachments that enable semi-automatic weapons to be fired rapidly.

A bump fire stock that attaches to a semi-automatic rifle to increase the firing rate is seen at Good Guys Gun Shop in Orem, Utah, on Oct. 4, 2017. George Frey/Reuters
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