Bilateralism may be defined as agreements between two countries to reserve the carriage of specific cargoes to a designated number of participants, principally but not always, national-flag fleets. They are legal instruments of the participating governments, specifying the commercial rights and the responsibilities of the national-flag fleets of each country in their bilateral trade. Bilateral agreements may involve revenue pooling agreements and sharing, on an agreed basis, the movement of specific commodities in the ships of the two trading partners.