When the other party has good reason to believe that the agent has authority, the act of agency can be treated as valid. Good reason exists when, based on all the circumstances at the time of the unauthorized act, an ordinary person would objectively believe the agent had authority, and the other party acted in good faith and without negligence. So for apparent authority to arise, the other party must have good reason to believe the apparent agent had the authority, and whether good reason existed in the case of acts beyond authority is judged as of the time of the act. Apparent authority for acts beyond authority also applies to legal agency.

Apparent authority after the end of authority, under Article 129, is recognized to protect a good-faith, non-negligent counterparty when a person whose authority has ended still acts as an agent. Even though the authority has ended, the law gives the same effect as if it existed in relation to the other party, so the end of authority cannot be asserted against that third party. For Article 129 to apply, authority that once existed must have ended. It covers only cases where the grant was revoked or the underlying internal relationship ended; where there was never any authority, apparent authority cannot

arise. The Supreme Court recognizes as a basis of authority not only cases where the former agent deals with the other party directly after the authority ends, but also cases where the former agent appoints a sub-agent after the authority ends.

If the other party did not know that the authority had ended, believed the sub-agent had valid authority and was not negligent, apparent authority under Article 129 arises in this case too. This can be seen as the doctrine of apparent authority recognizing good reason where someone created an appearance, for the sake of secure transactions. The principal bears the burden of proving the other party's bad faith or negligence. Because whoever disputes the effect bears the burden on good faith, this applies to all types of apparent authority. Whether Article 129 also applies to legal agency is debated, and the majority view applies it to legal agency to protect the other party.

This paper reviewed the agency system in the Korean Civil Code as a whole. Messengers and representatives are similar concepts, but agency differs in that it can produce effects directly for the principal even if the agent lacks full legal capacity. And besides authorized agency, even unauthorized agency can become a valid juristic act if certain requirements are met and the principal ratifies it. In this way agency protects secure transactions, the other party and third parties, so its social meaning is very important. Voluntary agency extends private autonomy, and legal agency supplements the rules on persons lacking capacity, letting legal effects belong to someone other than the person who made the declaration, which makes it even more important. And because some forms of apparent authority are recognized for unauthorized agency, a juristic act can be validated retroactively by the principal's ratification.

However, ratification can also be excluded by agreement between the principal and the other party, and where rights acquired by the other party and by a third party both have exclusive effect, ratification cannot harm the third party's rights. Unless the principal ratifies, unauthorized agency has no effect on the principal, and the principal may actively refuse ratification. Against these rights of the principal, the other party has only the right to demand an answer and the right to withdraw, and depending on the outcome, the unauthorized agent bears no-fault liability to the other party and must, at the other party's choice, either perform the act or pay damages.

To add: the last sentence of the conclusion needs correcting. In unauthorized agency that the principal has not ratified, the person liable to perform or pay damages at the other party's choice is the unauthorized agent, not the principal (Civil Code Article 135(1)), and there is no such liability if the other party knew or could have known the lack of authority, or if the unauthorized agent has limited capacity (Article 135(2)). The term persons without capacity used in the paper was replaced by persons with limited capacity through the Civil Code revision that took effect in July 2013. The courts apply the proviso of Article 107(1) by analogy to abuse of authority.