Agency behaviors prohibited by law include the following three situations:
 1. Acting by yourself. Self agency means that an agent conducts civil acts on his own in the name of the principal. In this case, the agent is the agent and the third person in the agency relationship, and the transaction behavior of both parties is actually carried out by only one person.
 2. Agents of both parties. Agency of both parties is also called simultaneous agency, which means that it is a civil act for one person to act as the agent of both parties at the same time.
 3. The agent and a third party maliciously collude to conduct acts that harm the principal's interests
 [Legal Basis]
 Article 154 of the Civil Code states that a civil legal act that the perpetrator maliciously colludes with the counterpart and damages the legitimate rights and interests of others is invalid.