In Japan a lot of kofun including the Emperor Nintoku Mausoleum which are considered as graveyards of the Imperial Family are under control of the Imperial Household Agency; thus, excavation and research are not easily permitted, and this is one of the reasons for delayed archaeological study.
日本では仁徳天皇陵など皇室の墓所と比定されている多くの古墳は現在宮内庁の管理下にあり発掘調査許可がなかなか下りない事が考古学研究が遅れる要因の一つとなっている。