The Committee for Cultural Policy's (CCP) recent newsletter features an in-depth article explaining the history of the U.S. Memorandum of Understanding (MOU) and how it has been expanding in scope since 1999.
The request will be considered by the Cultural Property Advisory Committee, meeting at the Department of State on October 23-24, 2017.
From the CCP article:
The first Cambodian ban took effect on December 2, 1999, when the U.S. imposed an emergency import restriction on Khmer stone sculpture and architectural elements from Cambodia, unless such objects were accompanied by export permits issued by the Government of the Kingdom of Cambodia, or by documentation demonstrating that they were out of the country before December 2, 1999.