One of my partners is the trustee of an ESOP and the plan sponsor of the ESOP is in bankruptcy. What are his fiduciary duties now that the plan sponsor is in bankruptcy? Are his duties the same as they were before filing for bankruptcy?

His duties are the same as before the bankruptcy (with a lot more stress/risk). He needs to make decisions in the best interests of the plan participants. The bankruptcy trustee for the corporation will be charged with the mission of maximizing the recovery of assets for the interest of the creditors. The ESOP as a shareholder is at the end of the line for payments. The ESOP may have a higher priority is there are contributions due it. Your partner needs to battle the bankruptcy trustee to try to get some value for the shares (or if a chapter 11 reorganization to resist dilution of the ESOPs position).