"Federal workers are not allowed to volunteer to do their jobs during a shutdown because U.S. law says they can't do any work that has not been allocated funding.
The search effort had already begun being scaled back due to rescue agencies being called back to their respective headquarters and poor weather earlier in the week. Only three staff members are at the park monitoring infrastructure resources."
http://www.kboi2.com/news/local/Craters-Moon-Idaho-Jo-Elliott-Blakeslee-Amy-Linkert-225988051.html
