US President Donald Trump’s Justice Department is using the shooting at the White House Correspondents’ Dinner on Saturday to try to pressure preservationists to drop their lawsuit over his planned US$400 million ballroom on the site of the former East Wing of the White House.

“It’s time to build the ballroom,” acting Attorney General Todd Blanche said plainly on Sunday on social media, posting a letter in which Assistant Attorney General Brett Shumate gave the National Trust for Historic...