To revoke the press credential off CNN sounds like a good idea and is probably legal. Good for the Trump administration.
I'll tell you what is legal.
" Federal Marshalls, Federal Agents, escort the representatives of CNN out of the White House. "
Direct order from the President? CNN people are going to go. Federal Judge bitches? Too bad, so sad. The President does not have to answer to Federal Judges about who he allows into the White House, or on the White House grounds.