Call or Play Based on Player's Own Misunderstanding
No rectification or redress is due to a player who acts on the basis of his own misunderstanding.
Call Based on Misinformation from an Opponent
Until the end of the auction period (see Law 17D) and provided that his partner has not subsequently called,
a player may change a call without other rectification for his side when the Director judges that the decision to make the call could well have been influenced by misinformation given to the player by an opponent. Failure to alert promptly where an alert is
required by the Regulating Authority is deemed misinformation.
The Director is to presume Mistaken Explanation rather than Mistaken Call in the absence of evidence to the contrary.
When a player elects to change a call because of misinformation (as in 1 preceding), his LHO may then in turn change
any subsequent call he may have made, but Law 16C applies.
When it is too late to change a call and the Director judges that the offending side gained an advantage from the irregularity, he
awards an adjusted score.