Those agreements, partial or collective, that are in force between watercourse States regarding the utilization of the watercourse. For example, under international law rules on succession in treaties, existing agreements continue into force, irrespective of all conditions and changes. These agreements cannot be unilaterally modified, amended or nullified, and unless otherwise agreed, all future agreements, including the 1997 United Nations Convention on the Law on Non-navigational Uses of International Watercourses, are without prejudice to existing agreements. However, watercourse States have the right to negotiate a new agreement or agreements on the utilization and protection of the watercourse.