So deadly it’s considered a terrorist threat, carfentanil has been legal in China — until now. Beijing is banning carfentanil and three similar drugs as of March 1, China’s Ministry of Public Security said Thursday, closing a major regulatory loophole in the fight to end America’s opioid epidemic.“It shows China’s attitude as a responsible big country,” Yu Haibin, the director of the Office of the National Narcotics Control Committee, said. “It will be a strong deterrent.”