In November 2018, an event in American politics involved a certain reporter for CNN, Jim Acosta, having his press credentials revoked by the White House, thereby barring his access to the White House press conferences. My immediate and admittedly ignorant impression is that the president has no duty to hold press conferences and can therefore allow or disallow any party's attendance.
CNN and many other news organizations apparently see it differently, resulting in a lawsuit naming the president himself, among others, for both 1st amendment and 5th amendment violations. To my surprise, a judge agreed and ordered the White House to immediately reinstate Jim Acosta's press credentials.
The lawsuit also charged that there is a procedure for removing press representatives, and that this procedure was not followed. With my understanding being that the president has no duty to hold press conferences in the first place, to what extent does the White House have a duty to follow a procedure when admitting or barring specific press representatives to White House press conferences? Are there rules, laws, or just precedents based on previous presidential actions? To extend further to the president personally, to what extent is the president's duty to entertain any press person at any specific time or place?