20880302_ferences__July_2014_FIDE_Laws___FIDE_rule
[0] 1. [USCF rule] Only the players may call a fallen flag. [FIDE rule] 
The arbiter can call fallen flags without a claim by the player or the opponent.
The United States Chess Federation - USCF - FIDE Rule Differences (July 2014 FIDE Laws)
FIDE rule