a person remains under detention depends largely on the Ministry of Home Affairs. This raises the question quis custodiet ipsos custodes? – who guards the guardians? If preventive detention is applied illegitimately in a manner that cripples lawful democratic opposition, the absence of judicial review would preclude the exposure of such abuse. It has been submitted that the voice of public opinion is most suited for this purpose. Instances of the application of the PPSO and ISA According to The Sunday Times of 28 October 1956, 234 people, including trade union leaders Lim Chin Siong, James Puthucheary and C. V. Devan Nair, were detained under the PPSO as suspected Communist subversives. On 2 February 1963 Operation Coldstore, a joint Malaysian–Singaporean anti-Communist operation, led to the arrest of 133 people. As of 5 April 1963, 17 were being detained in the Federation of Malaya and 107 in Singapore, while the remaining nine had been released. On 30 October 1966, Chia Thye Poh, leader of the leftist Barisan Sosialis political party, was detained. He was subsequently held for 32 years pursuant to the ISA, the last nine of which under forms of house arrest and civil rights restrictions, including confinement on the island of Sentosa. All such restrictions were finally lifted on 27 November 1998. As of that date, the South China Morning Post referred to him as "the world's second longest serving prisoner-of-conscience after South Africa's Nelson Mandela". The Straits Times of 28 May 1976 reported that 50 people allegedly involved in a Communist plot had been arrested. Among them were the playwright and theatre director Kuo Pao Kun, then a secretary for the Chinese Chamber of Commerce, and his wife Goh Lay Kuan. Kuo was detained under the ISA for four years and seven months, and his citizenship was revoked. Following his release he was placed under residence and travel restrictions until 1983. His citizenship was reinstated in 1992. In 1987, in a security operation known as Operation Spectrum, 22 Roman Catholic church and social activists and professionals were detained under the ISA. They were accused of being members of a dangerous Marxist conspiracy bent on subverting the government by force and replacing it with a Marxist state. The detentions led to, among others, the Chng Suan Tze and Teo Soh Lung cases. Two people were arrested in 1997 and four in 1998 for espionage activities. Of those arrested in