This chapter explores the procedural constraints that investment tribunals face when independently ascertaining the law. At the same time, these constraints serve as safeguards for the parties’ procedural rights. If tribunals fail to adequately protect these rights, the risk of annulment or unenforceability of the award increases—even though such outcomes have been rare in practice. This chapter focuses on the following procedural constraints: ne ultra petita, the right to be heard, impartiality and the requirement to provide a reasoned award.