East Asia was stunned last week when the China National Offshore Oil Company (CNOOC) moved its most advanced drilling rig to a gas and oil block 120nm from the coast of Vietnam. Reportedly protected by dozens of Chinese coast guard ships and – according to some reports – navy ships, the move caught Hanoi off guard. Vietnam quickly dispatched its own coast guard ships to confront the Chinese, which resulted in several collisions within the 3nm exclusion zone around the rig. Vietnam’s options are constrained by its lack of military allies, ASEAN disunity and its relative naval weaknesses vis-à-vis China. Nevertheless, it cannot condone unilateral Chinese drilling in its Exclusive Economic Zone. In addition to its considerable diplomatic campaign to isolate China, the government of Vietnam should take CNOOC to court in Vietnam in response to China’s move.