China’s foreign ministry sent out a new travel advisory last week, telling its citizens to be prepared for what it called “various unexpected situations” when they enter U.S. customs. And the U.S. government also suggested that American citizens reconsider travel to mainland China. A statement explains that’s due to “arbitrary enforcement of local laws,” including “exit bans, and the risk of wrongful detentions.” In one case, an American executive has been stuck in mainland China for 6 years as of today, under an exit ban issued by the Chinese authorities.