Immediately after Trump took the oath of office on Friday, Citizens for Responsibility and Ethics in Washington filed a complaint
with the General Services Administration and called on the federal
government to notify the new president that he was officially in
violation of his lease for the Trump International Hotel down the street
from the White House. The lease that one of Trump’s company’s, Trump
Old Post Office LLC, signed with the government states that no “elected
official” of the U.S. government can share in the lease or derive
benefit from it.

(via Live Coverage of Donald Trump’s Inauguration – The Atlantic)