Bren Guiao began his writing career at the Luzon Courier in Pampanga before serving as a delegate to the 1971 Constitutional Convention.
Marcos explored various options to extend his term in office. Changing the 1935 Constitution was seen as one such opportunity to do so. Philippine Free Press Writer Edward Kinansala reported an increasing politicization of the Convention early in 1972. Delegates to the convention had allegedly been bribed to shift from a Presidential to a Parliamentary government, and Friar-delegate George Kintanar made note of 10 delegates who had travelled to Malacanang and were given “10,000 reasons” to support the shift. Bren and other representatives who formed the opposition group of the Constitutional Convention sought investigations into the matter, including the release of Kintanar’s list of delegates supposedly under the Palace payroll.
One of the delegates, Eduardo Quintero, a former ambassador and province mate of the First Lady Imelda Marcos, later revealed that he and other delegates had indeed received envelopes filled with money to persuade them to lobby the shift to a Parliamentary government. Marcos turned on Quintero, who single-handedly revitalized opposition towards the Constitutional Convention and raised red flags for the people. Former Marcos propagandist Primitivo Mijares would also recount being tasked to dig up “dirt” on Quintero and delegitimize his claims. Charges were filed and a raid on Quintero’s home was made, allegedly finding a huge sum of money. Though Quintero and the opposition delegates garnered much support, the effect of this revelation would be tempered in September of 1972.
Bren was immediately detained after Martial Law was declared. Having been outspoken critics of the administration, he and ten other delegates to the Constitutional Convention were included in a pre-selected list of targets to be incapacitated by the regime. With dozens of its members imprisoned or in hiding, and the threat of arrest looming over those who remained, the participants in the Convention swiftly passed a new constitution which further expanded Marcos’ executive and legislative powers.
Bren would be released under a number of conditions similar to those imposed upon co-detainees. He was to sign an oath promising not to participate in anti-national activities. He would be barred from resuming work without obtaining a permit from the army, and required to report periodically to the army – effectively placing him under house arrest. He was also barred from giving or participating in any interview with any local or foreign media correspondents for any publication, news, TV or radio broadcast.
 Sangil, Max (24 June 2020), “Pampanga newsmen in the fifties and onward”. Sunstar. Retrieved from https://www.sunstar.com.ph/article/1861252/Pampanga/Opinion/Pampanga-newsmen-in-the-fifties-and-onward
 Kinansala, Eduard (22 January 1972), “The Politicalization of the Constitutional Convention”. The Philippine Free Press. Online copy retrieved from https://philippinesfreepress.wordpress.com/1972/01/22/the-politicalization-of-the-constitutional-convention-january-22-1972/
 Mijares, Primitivo (1976), The Conjugal Dictatorship of Ferdinand and Imelda Marcos. Martial Law Chronicles Project. Online copy retrieved from https://martiallawchroniclesproject.com/wp-content/uploads/2017/07/The-Conjugal-Dictatorship-of-Ferdinand-and-Imelda-Marcos.pdf, 53, 138; Robles, Raissa (2016) Marcos Martial Law: Never Again. Quezon City: Filipinos for a Better Philippines, 34.
 Magno, Alexander R., ed. (1998). “Democracy at the Crossroads”. Kasaysayan, The Story of the Filipino People Volume 9:A Nation Reborn. Hong Kong: Asia Publishing Company Limited.
One of the opposition delegates, Augusto Caesar Espiritu, recounts of the delegates arrested in his book
Espiritu, A. C. (1993). How democracy was lost : a political diary of the Constitutional Convention of 1971-1972. Quezon City: New Day Publishers.
The other delegates detained were Teofisto Guingona, Ernesto Rondon, Jose Concepcion, Jr., Jose Nolledo, Alejandro Lichauco, Natalio Bacalso, Jose Mari Velez, Napoleon Rama, and Antonio Araneta, Jr.
 In the matter of petition for habeas corpus of Benigno S. Aquino v Juan Ponce Enrile.
GR No. L-35546, Sep 17, 1974.