Section 14-121. Details to special duty

A transfer, detail or assignment to
  special duty of any member of the force, except in cases  authorized  or
  required  by  law,  shall not hereafter be made or continued, except for
  police  purposes  and  in  the  interests   of   police   service.   The
  commissioner,  however,  whenever the exigencies of the case require it,
  may make a detail to special duty for a period not exceeding three days,
  at the expiration of which the  member  or  members  so  detailed  shall
  report  for duty to the officer of the command from which the detail was
  made.