CHAPTER VI
The Play 

PART V
CLAIMS AND CONCESSIONS

LAW 71 - CONCESSION CANCELLED 

A concession must stand, once made, except that within the correction period established in accordance with Law 79C, the Director shall cancel a concession:

A. Trick Cannot be Lost

If a player has conceded a trick his side had, in fact, won, or a trick his side could not have lost by any legal play of the remaining cards.

B. Contract Already Fulfilled or Defeated

If declarer has conceded defeat of a contract he had already fulfilled, or a defender has conceded fulfillment of a contract his side had already defeated.

C. Implausible Concession

If a player has conceded a trick that cannot be lost by normal play of the remaining cards. Until the conceding side makes a call on a subsequent board, or until the round ends, the Director shall cancel the concession of a trick that could not have been lost by any normal play of the remaining cards.