According to the provisions of Articles 65 and 66 of the General Principles of the Civil Law and Article 81 of the Opinions of the Supreme People's Court on Several Issues of Implementation, there are several cases of joint liability for agency: 1. If the power of attorney is unclear, the principal shall bear civil liability to the third party, and the agent shall bear joint liability. 2. If an agent colludes with a third person to damage the principal's interests, the agent and the third person shall be jointly and severally liable; If a third party knows that the actor has no power of agency, has exceeded the power of agency or has terminated the power of agency, but still performs civil acts with the actor, causing damage to others, the third party and the actor shall be jointly and severally liable. 3. If an entrusted agent entrusts another person to act as his agent and causes losses to a third person because his delegation is unclear, the third person may directly demand the principal to compensate for the losses. After the principal bears civil liability, he may demand the entrusted agent to compensate for the losses. If the entrusted agent is at fault, he shall be jointly and severally liable. How are the relevant laws on agency stipulated in the civil law? Article 63 of the General Principles of the Civil Law of the People's Republic of China: Citizens and legal persons may perform civil legal acts through agents. An agent shall, within the scope of his power of agency, perform civil juristic acts in the name of the principal. The principal shall bear civil liability for the agent's act of agency. Article 66 of the General Principles of the Civil Law of the People's Republic of China: The principal shall bear civil liability for acts without agency power, beyond the agency power or after the termination of the agency power only after the principal's ratification. The actor shall bear civil liability for acts not ratified. If I know that another person has committed a civil act in my own name without denying it, it shall be deemed as consent. Article 48 of the Contract Law of the People's Republic of China: A contract entered into by an actor in the name of the principal without ratification by the principal without the actor's power of agency, beyond the power of agency, or after the termination of the power of agency, shall have no effect on the principal, and the actor shall be liable. The opposite party may demand the principal to ratify it within one month. If the principal fails to make any indication, it shall be deemed that he has refused to ratify. Before the contract is ratified, the bona fide counterpart has the right to cancel it. Cancellation shall be made by notice. Article 49 of the Contract Law of the People's Republic of China: If the actor has no agency power, exceeds the agency power or enters into a contract in the name of the principal after the termination of the agency power, and the counterpart has reason to believe that the actor has the agency power, the agency act is valid. Article 58 of the Opinions of the Supreme People's Court on Several Issues of Implementation: If the legal representative and other staff of an enterprise legal person conduct business activities in the name of a legal person and cause economic losses to others, the enterprise legal person shall bear civil liability. The above is about the circumstances under which the trustor and the trustee bear joint liability? What is the legal basis? Have you learned the knowledge of law?