Stern punishments of independence-seeking demonstrators, rioters, or terrorists have led to mistreatment of the Tibetan and Uyghur minorities in Western China. The United States in 2007 refused to help repatriate five Chinese Uyghur Guantanamo Bay detainees because of 'past treatment of the Uigur minority'. In its 2007 annual report to the U.S. Congress, the Congressional-Executive Commission on China said the Chinese government "provides incentives for migration to the region from elsewhere in China." Xi Jinping, the General Secretary of the Chinese Communist Party (paramount leader), said in April 2014 that China faces increasing threats to national security and the government could impose tougher controls on its ethnic minorities due to terrorist attacks like the 2014 Kunming attack. In Xinjiang, the Ürümqi Motorized Vehicle Licensing and Testing Department has begun requiring all ethnic Uyghur and Kazakh individuals to undergo a background check before registering a vehicle.