There can be no Constitutional right for employees of a corporation to show up at the White House and demand admittance to a press conference. None of these people have any more right to be there than we do as private citizens.
This reminds me of a scene from the show “Lioness”.
Where Nichole Kidman’s character(CIA Agent) is late for a meeting at the White House. When she enters it she says:
“You can take an eight ball into the west wing, but God help you if you forget your driver’s license.”