World Chess Federation - FIDE

World Chess Federation - FIDE: "A player may stop the clocks only in order to seek the arbiter’s assistance, for example when promotion has taken place and the piece required is not available.
c.The arbiter shall decide when the game is to be restarted in either case.
d.If a player stops the clocks in order to seek the arbiter’s assistance, the arbiter shall determine if the player had any valid reason for doing so. If it is obvious that the player had no valid reason for stopping the clocks, the player shall be penalised according to Article 13.4.
6.13If an irregularity occurs and/or the pieces have to be restored to a previous position, the arbiter shall use his best judgement to determine the times to be shown on the clocks. He shall also, if necessary, adjust the clock’s move counter."