When Björk yelled "Tibet! Tibet!" at a concert in Shanghai earlier this year, she might as well have been shouting "O Chinese government - crack down on foreign artists!" Though the state's initial response was just to rebuke the Icelandic singer, they have now implemented new policies to guard against musicians who "threaten natural unity". China will not just be screening artists' work visas - they will even be screening setlists.

"Any artistic group or individual who has ever engaged in activities that threaten our national sovereignty will not be allowed in," the Ministry of Culture announced in a statement. Artists from Hong Kong, Taiwan and overseas will be under particular scrutiny.

China has already banned pop festivals and restricted outdoor events in the lead-up to this summer's Olympics, fearing protests or simply unruly crowds. Björk seemed to have protesting in mind when she performed her song Declare Independence in March, throwing Tibet's name into the mix.

China has occupied Tibet since the 1950s, calling it their own rightful territory. The Tibetan independence movement - long active on the world stage - has received renewed attention in advance of the 2008 Beijing Olympics.

China has now promised to ban any performer who "threatens national unity", "whips up ethnic hatred", "violates religious policy or cultural norms" or "advocates obscenity or feudalism and superstition". These conditions are sufficiently vague that we suspect Ringo Starr could be banned, say, just for singing of a superstitious Octopus's Garden. The Ministry of Culture will also be reviewing setlists for hints of trouble - for example, any songs called Declare Independence. Even encores will be subject to government scrutiny. "Nothing that has not been approved will be allowed to be performed," they have stated.

Björk is not the only recent musician to face Chinese hostility - she was simply the only famous one. Several Asian artists have been rebuked by the government, notably the Taiwanese pop star Chang Hui-mei. Banned from China for her support of an independent Taiwan, Hui-mei was later re-admitted to the country - possibly when Chinese authorities remembered how head-over-heels gobsmackingly popular she is.

Barring Björk's reinvention as a safe, sappy Chang Hui-mei-style singer, it seems unlikely that she will ever again come within snowball-throwing distance of the Forbidden City. Maybe she can plan a trip to Chechnya instead.