The president named Todd Blanche, the deputy attorney general, as the acting librarian. But staff members refused access to two department officials he chose for key roles at Congress’s main research arm.

President Trump on Monday named the No. 2 official at the Justice Department and his former personal lawyer to serve as the acting librarian of Congress, initiating a shake-up at the main research library of the legislative branch that prompted an instant revolt among the staff.

Mr. Trump named Todd Blanche, the deputy attorney general who was his lead defense lawyer in his criminal trial in Manhattan last year, to take over from Carla Hayden, the librarian of Congress whom the president abruptly fired late last week.

But staff members at the Library of Congress pushed back, insisting that Congress must have input and refusing to give two other top Justice Department officials whom Mr. Blanche chose for senior positions there access to the agency’s headquarters on Capitol Hill, according to two people familiar with the situation.

The lockout led to a brief standoff across from the Capitol and became the latest flashpoint in a battle over where Congress’s authority ends and the White House’s begins.