On 23 June 2009, the United States requested consultations with China with respect to China's restraints on the export from China of various forms of raw materials. 

China justified these measures by the conservation of natural resources. This necessity allows for a restriction under GATT article XX(g).

The Appellate Body upheld the Panel’s finding that there is no basis in China’s Accession Protocol to allow the application of Art. XX to China’s obligations under para.11.3 of the Protocol. The Panel had concluded that China’s export restraints were not justified pursuant to Arts. XX(b) and (g). These findings were not appealed. In this context China only appealed the Panel’s interpretation of the phrase “made effective in conjunction with” in Art. XX(g). The Appellate Body concluded that the Panel erred and stated that these terms mean that the export restrictions and the restrictions on domestic consumption or production “must “work together”.

Based on: https://www.wto.org/english/tratop_e/dispu_e/cases_e/1pagesum_e/ds394sum_e.pdf

https://www.wto.org/english/tratop_e/dispu_e/cases_e/ds394_e.htm