Mr. Trump can prevent Mr. Biden and his aides from receiving the presidential daily briefing, the compendium of the government’s latest secrets and best intelligence insights, for the entire transition. No law states that Mr. Biden must receive it, though under previous administrations dating to at least 1968, presidents have authorized their elected successors to be given the briefing after clinching victory.

Previous presidents considered it good governance, said David Priess, a former C.I.A. officer and the author of “The President’s Book of Secrets,” about the daily brief…

Along with the presidential daily briefing, transition team officials need to have access to classified information at intelligence agencies, like the C.I.A., to make staffing decisions and begin planning for the administration.

On this front, Mr. Trump can make it much more difficult for the Biden team to gain access to those materials. Under law, the Trump administration must formally recognize Mr. Biden as the president-elect to share classified information with his team. That decision is typically made by the head of the General Services Administration, a little-known government agency that oversees the transition. The head of that agency, Emily W. Murphy, is a Trump political appointee who so far has declined to designate Mr. Biden as the president-elect. As long as the G.S.A. refuses to recognize Mr. Biden, the team cannot legally view the materials.