Works of the U.S. government are in the public domain. Yet this notice accompanies White House photographs posted at flickr:

“This official White House photograph is being made available only for publication by news organizations and/or for personal use printing by the subject(s) of the photograph. The photograph may not be manipulated in any way and may not be used in commercial or political materials, advertisements, emails, products, promotions that in any way suggests approval or endorsement of the President, the First Family, or the White House.”

Awkward language aside (what is “for personal use printing by the subject(s) of the photographs”?) the restrictions are unenforceable.