Shippers’ councils. When liner conferences were formed they represented the ocean carriers and whether or not they exercised monopoly power, they still presented a negotiating group that had strong bargaining power.
Sub-letting. It is customary to stipulate in a time or voyage charterparty that charterers have the right of sub-letting the whole or part of the vessel on the understanding, however, that they remain responsible to the shipowners for the due fulfilment of the original charterparty. In the case of a voyage charterparty, sub-letting will probably take the form of booking other cargo by charterers.
Subject approval of relevant authority. This affects the enforceability of a charter if the ship's certification and cargo handling capabilities are required to meet with official approval. For example, if a vessel is not provided with a valid "document of authorisation" it may not be allowed to load grain and the charter may depend on permission being granted to load.