Article 23 A patent agent shall not accept the entrustment of an interested party on patent affairs with the same content after dissolving the entrustment relationship with the principal according to law.
Article 18 A patent agent shall not accept the entrustment of two or more interested parties on patent affairs with the same content.
The key is what is "patent affairs with the same content"?
Personal understanding:
1. If C requires that A's patent for B is invalid, A can accept the entrustment if it is not represented by A;
2. no.