I'm a little late getting to this story, but a federal judge ruled last week that it was not a First Amendment violation for the Governor of Maine to order the removal of a mural from a state Labor Department office:
"Elected state leaders ... have the right to decide what to say and what not to say, and by extension during their term in office, they are authorized to decide what the state of Maine says or does not say about itself. State of Maine Governor Paul LePage’s removal of a mural from the walls of a state office because he disagreed with its contents may strike some as state censorship; instead, it is a constitutionally permissible exercise of gubernatorial authority. Though his action provoked a storm of constitutionally-protected speech with a stark division between those who applauded his decision as rebalancing the state of Maine’s message to the business community and those who condemned his action as muzzling opposing viewpoints, the resolution of this vigorous debate must not rest with judicial authority of a federal court. It must rest instead with the ultimate authority of the people of the state of Maine to choose their leaders....
"It is not the business of the federal court to decide what messages the elected leaders of the state of Maine should send about the policies of the state, to tell a prior administration that its own artwork is too slanted to continue to hang on state office walls, to tell the current administration that it must not remove or replace a prior administration’s artwork, or to tell a future administration which piece of state art, the new or the old, must stay or go. The messages from the state-owned works of art are government speech and Maine’s political leaders, who are ultimately responsible to the electorate, are entitled to select the views they want to express."
Lawprof Eugene Volokh says that "sounds quite right." News story here. A question from Sergio Muñoz Sarmiento here.
