Statutes of the student body
The statutes of the student body regulate the organization and tasks of the student body in accordance with the BerlHG. It also regulates the bodies of the university such as the AStA. Among other things, it specifies the number of members and the structure of the executive board. It also specifies how the AStA is to work and how it cooperates with the student parliament.
You can read the statutes here.