Via the AAUP’s Academe Blog, here’s the background:
On December 3, authorities detained 20 labor activists in Guangdong Province. Four have been placed under criminal charge, several are unaccounted for, and the rest have been questioned and released. All of these activists are associated with four grass-roots labor NGOs in the Pearl River Delta. This campaign of unprovoked suppression has once again put into profound question the abuse of government authority in China. A “sweep” such as this is intended to terrorize and intimidate, not enforce a system of judicious rules; it is the use of government power to bully.