The Maritime Safety Committee (MSC) of International Maritime Organization (IMO), at its 98th session held on June 2017, agreed to include a new agenda item “Regulatory scoping exercise for the use of Maritime Autonomous Surface Ships (MASS)” in order to determine how the safe, secure and environmentally sound operation of MASS may be introduced in IMO instruments. In the regulatory scoping exercise, it is necessary to identify IMO regulations: (1) which preclude unmanned operations; (2) which would have no application to unmanned operations; and (3) which do not preclude unmanned operations but may need to be amended for enabling the construction and operation of MASS. The purpose of this investigation is to identify IMO regulations attributed to the aforementioned cases, in order to contribute to the work of the MSC. Specifically, regulations in the International Convention for the Safety of Life at Sea (SOLAS Convention) are investigated. The SOLAS Convention makes many IMO instruments mandatory in its text. Requirements in the IMO instruments which are made mandatory by the SOLAS Convention are also investigated. Based on the results of the investigation, suggestions for research and development of unmanned ships are considered.