China is increasingly turning to visa cancellation to threaten and manipulate foreign businessmen and professors operating in the country. The tactic has led to growing concern that intellectuals might censor themselves in order to maintain access to China, and some Americans have been calling for the United States to pressure China to back off. When Elliot Sperling, an American professor, landed in Beijing at the start of July with a valid 1-year tourist visa, he was promptly marched into a back room and interrogated before being put back on the plane he'd arrived on and sent home - visa cancelled. Why? Mr. Sperling said he believed he was being punished for his vocal support of Ilham Tohti, an ethnic Uighur economics professor here who has been charged by the Chinese authorities with separatism, and whose arrest has ignited outrage across the globe. In interviews with the NY Times, Mr Sperling has maintained that "The issue for me is not my being denied entry — I can certainly continue my research and academic work without going to China — but the attempt to pressure those who speak in support of Ilham to retreat into silence, or at least to isolate them. I have done nothing wrong except to dissent — vociferously, I admit, but still I use only words — and have no intention of conforming to authoritarian norms for the sake of a visa."