It's on. The announcement from CNN:

CNN filed a lawsuit against the Trump Administration this morning in DC District Court. It demands the return of the White House credentials of CNN’s Chief White House correspondent, Jim Acosta. The wrongful revocation of these credentials violates CNN and Acosta’s First Amendment rights of freedom of the press, and their Fifth Amendment rights to due process. We have asked this court for an immediate restraining order requiring the pass be returned to Jim, and will seek permanent relief as part of this process. While the suit is specific to CNN and Acosta, this could have happened to anyone. If left unchallenged, the actions of the White House would create a dangerous chilling effect for any journalist who covers our elected officials.

The White House Correspondents' Association backs up their members: