Barrett was involved in the Constitutional Rights Campaign, which unsuccessfully campaigned to prevent the ratification of the Single European Act in 1986. In 1987 he became involved in Family Solidarity, a movement established to oppose liberalisation on social issues such as abortion, contraception, gay rights and divorce. Lack of success in this area led him to the conviction that political involvement was necessary for results - he was subsequently involved in Young Fine Gael until 1991. From 1992 he became actively involved in the Irish pro-life movement, becoming the lead spokesperson of Youth Defence, and as a student in Athlone RTC he unsuccessfully contested the election for the Presidency of Union of Students in Ireland. During the 1995 divorce referendum, he was spokesman for the Youth Against Divorce campaign. He was also involved in the campaign against the 2002 abortion referendum.
In 2001, Barrett campaigned against the Nice Treaty referendum - a vote which was subsequently held again and was approved. During the second Nice campaign, Barrett became the centre of a controversy over links to alleged "neo-Nazi" movements in Germany. Barrett admitted he had spoken at a NPD rally, but denied he had any sympathy with their policies and said that he had addressed the rally only in his capacity as a pro-life campaigner.
European Parliament elections 2004
In the European Parliament election, 2004, Barrett ran for a seat in the 'East' constituency, but only managed 2.4% of the vote (a total of 10,997 first-preference votes). Later that year, while attending a debate in University College Dublin, Barrett claimed he was the victim of an assault by members of the Irish Anti-Fascist Action group.
Justin Barrett is married with three children.
He published a book putting forth his political principles, entitled The National Way Forward!  In the book he described immigration as "genocidal" and said that he was influenced by Hilaire Belloc, G. K. Chesterton and Arthur Penty. He also promoted the work of Father Denis Fahey.
- Millar, Scott (12 January 2010). "Irish far right groups remain on the margins of political life". Irish Examiner. "...former Youth Defence leader, Justin Barrett."
- Gable, Gerry (November 2009). "Jim Dowson: How a militant anti-abortionist took over the BNP. Part 1 of a three part investigation.". Searchlight. "His luck changed when he formed an alliance with Justin Barrett, a far-right Catholic lawyer and leader of the notorious Irish anti-abortion group Youth Defence, which had previously stormed buildings in Dublin in their crusade against a woman's right to choose."
- [http://www.independent.ie/opinion/analysis/the-man-wired-to-fight-abortion-26251153.html The man wired to fight abortion Irish Independent
- Barrett admits attending far-right party meetings in Italy, Germany — Irish Times story, 12 October 2002
- Donaghy, Kathy (12 October 2002). "Campaigners on both sides of treaty lash out at Barrett". Irish Independent. Retrieved 13 December 2012.
- Elections Ireland: Justin Barrett — election results from 2004
- Justin Barrett 'Attacked' while attending UCD debate — from the Indymedia Ireland website
- Way forward is a huge, hysterical step back — Sunday Business Post book review, 15 June 2003
- Abortion fighter turns his sights on immigration, Scott Millar, The Times, 18 May 2009, retrieved 14 May 2009
- Ex-Provo gives new life to Irish clerical fascism Searchlight, August 2006