When accepting the entrustment of the parties and acting as an agent in arbitration proceedings, a lawyer shall sign an entrustment contract with the parties in the name of a law firm and participate in arbitration in the name of a lawyer. If you appear in court as a lawyer, you need a letter from a law firm to prove your identity as a lawyer. If the client and the lawyer are close relatives, they may not appear in court as lawyers, so there is no need for a lawyer's letter.