On 18 December 2005, Zen visited protesters at the 2005 WTO Ministerial Conference and tried to visit the detained South Korean Catholics, including two priests and a nun. He criticised the Hong Kong police for their treatment of the protesters. About one month later, several unions in Hong Kong Police Force decided to write a letter to the Pope to complain about Zen's speech. Zen replied that some policemen were "sycophantic to the senior officers inside the police force".