washington republican democratic u.s. congressmen introduce bill thursday would ban americans travel north korea tourists require obtain special permission type visit democrat adam schiff republican joe wilson say propose north korea travel control act follow detention least 17 americans north korea past decade north korea record use detain americans extract high-profile visit unite state formal diplomatic relations increase tensions north korea danger americans detain political reason great ever congressmen say statement give north korea demonstrate willingness use american visitors bargain chip extract high level meet concessions appropriate unite state take step control travel nation pose real present danger american interest say four americans hold north korea diplomatic tensions washington heighten two detain past month affiliate private university north korean capital congressional source say bill would ban tourist travel americans outright visit would require special license treasury department enforce wide range sanction north korea nuclear missile program north korea month assert sovereign right ruthlessly punish u.s. citizens detain crimes government say call arrest bargain ploys pure ignorance north korea say may detain kim hake song work pyongyang university science technology suspicion hostile act another american kim sing dok associate school detain late april charge two americans otto warmbier 22-year-old student detain january 2016 sentence 15 years hard labor attempt steal propaganda banner kim dong chul 62-year-old korean-american missionary kim sentence 10 years hard labor subversion last year u.s. bill would ban american tourist travel north korea