Commercial lawCommercial law, also known as mercantile law or trade law, is the body of law that applies to the rights, relations, and conduct of persons and business engaged in commerce, merchandising, trade, and sales. It is often considered to be a branch of civil law and deals with issues of both private law and public law. Commercial law includes within its compass such titles as principal and agent; carriage by land and sea; merchant shipping; guarantee; marine, fire, life, and accident insurance; bills of exchange, negotiable instruments, contracts and partnership.