"There must be decorum at the White House," declared White House Press Secretary Sarah Huckabee Sanders.
"With the rules and regulations, we will end up back in court and we will win," Mr. Trump said in a photo op.
The President made his comments just moments after CNN's Acosta returned to the White House, immediately after a federal judge appointed by the President had said that no legitimate reason had been given by the government for revoking his 'hard pass' to the White House.
Acosta could have - but did not - attend the photo op.
In a statement, the group representing reporters at the White House said Acosta's return was the correct move.
"The White House Correspondents' Association welcomes today's ruling, in which a federal judge made it clear that the White House cannot arbitrarily revoke a White House press pass."