Condonation
Condonation, or condonance may be made when an accuser has previously forgiven or condoned (in some way or at some level supported) the act about which they are complaining. In some legal jurisdictions, and for certain behaviors, it may prevent the accuser from prevailing.
Civil law
For example, if a creditor states that they forgive a certain debt, they might be blocked (or estopped) from attempting to collect that debt later. They would not be blocked from collecting any other debts, however. Condonation may also be a defense in cases of dismissal from employment for cause where the employer by word or conduct forgives or impliedly forgives behavior which would otherwise justify dismissal without notice.
On the other hand, condonation is irrelevant to some acts. For example, some jurisdictions prohibit fighting by consent (other than in specially-sanctioned sports, such as boxing). In such a jurisdiction, people arrested for brawling cannot avoid prosecution by condoning one another's assaults.
Military law
The principle of condonation in military law is traced back to the "Memorandum on Corporal Punishment" issued by the Duke of Wellington on 4 March 1832:[1]
"The performance of a duty of honour or of trust, after the knowledge of an offence committed by a soldier, ought to convey a pardon for the offence."
Divorce Law
Prior to the advent of no fault divorce statutes, condonation was frequently asserted as a defense to divorce. Although one spouse may have committed an act that justified the other in obtaining a divorce, the other spouse might be deemed to have forgiven the conduct and thus waived the right to sue for divorce. The most typical way in which condonation occurred is if the wronged spouse, with knowledge of the act, voluntarily engaged in sexual relations with the wrongdoer. Critics of the doctrine contended that it discouraged spouses from attempting reconciliation, as one act of sexual intercourse would deprive the wronged spouse of any relief if the spouses were unable to resolve their differences.