This paper reviews the recent regulatory developments relating to transboundary carbon dioxide capture and storage (CCS) activities and regulation of ocean fertilization and other marine geoengineering activities arising from the work and agreements under the London Protocol from 2010 to 2013. Geological storage of CO2 in transboundary sub-seabed geological formations is now possible and regulated under the London Protocol, but not yet the export of CO2 for geological storage in sub-seabed geological formation until an export amendment is ratified by two-thirds of the Parties to the London Protocol and comes into force. With marine geoengineering based upon placement of matter in the marine environment, the London Protocol has decided that such activities fall under its scope. It has considered and prohibited ocean fertilization except for research purposes only, and a procedure is provided for new marine geoengineering activities to be considered. For both activities, detailed guidance is provided on the assessments and conditions for issuing of permits.