All printing, binding, and blank-book work for Congress, the Executive Office, the Judiciary, other than the Supreme Court of the United States, and every executive department, independent office and establishment of the Government, shall be done at the Government Printing Office, except
(1) classes of work the Joint Committee on Printing considers to be urgent or necessary to have done elsewhere; and
(2) printing in field printing plants operated by an executive department, independent office or establishment, and the procurement of printing by an executive department, independent office or establishment from allotments for contract field printing, if approved by the Joint Committee on Printing. Printing or binding may be done at the Government Printing Office only when authorized by law.