Registration of Vessels dates back almost nine hundred years to the maritime laws of Oleron (Circa 1160) but became more relevant in the eras of piracy and colonial exploitation.
The original purpose of registering a ship under the national flag was to give that vessel the protection of the government whose flag the vessel flew as a sign of the nation to which it belonged. In Solomon Island Shipping Act 1998 there is still a section 7 that states where a vessel that is required to be registered under the act is not so registered, the vessel shall not be entitled-
More details of vessels registration in Solomon Islands are in the Shipping Act 1998 – from section 9 to 52 and shipping (registration) Regulation 2010
The modern purpose of ships registration is to establish a link between the owner and the state in which the vessel is registered, and to satisfy the United Nations Convention on the Law of the Sea (UNCLOS) which requires every vessel to be registered in a state, but it must not be registered in more than one state at a time. This is one reason why a Certificate of Deletion is so important. A vessel that is brought to Solomon Islands for registration must be removed from its former register before it can be registered in Solomon Islands.