[5] In 1998, he along with Arnaldo Otegi and Joseba Permach, came to public prominence after the previous leadership of Herri Batasuna (HB) were jailed for alleged links to ETA.

[12][2] Barrena and other leaders of Batasuna were arrested on the orders of judge Fernando Grande-Marlaska who held them responsible for attacks by the strikers.

[5] Barrena was a candidate at the 2007 regional election in Navarre for the Nafarroako Abertzale Sozialistak electoral alliance which was also annulled by the Supreme Court.

[14][15] Barrena and Urrutia were arrested on 4 February 2008 on the orders of judge Baltasar Garzón for "supporting the activity of an illegal political party".

[4] In April 2019 he was chosen by EH Bildu to be its leading candidate at the 2019 European Parliament election in Spain following the resignation of Josu Juaristi.