He is one of the group’s elders and maintains strong ties to Cuba, which has supported the guerrilla group since the 1960s. He has also opened the way for peace talks on several occasions, including trying to join government negotiations with the FARC in 2012, although the attempts have so far failed.
Gabino joined the ELN in 1964, at age 14, when the insurgency was but an idea in the moutainous province of Santander. In 1965, he participated in the ELN’s first military assaults in the municipality of Simacota, Santander. In 1973, he became part of the national leadership council (Direccion Nacional) after two founding members of the group died in battle.
In the late 1970s, he assumed joint leadership with Manuel Perez, alias "El Cura," the Spanish priest who had joined the group in the 1960s. After El Cura's death in 1998, Gabino became commander-in-chief of the ELN. He is considered the ELN’s main strategist and its elder statesman, having seen the group’s beginnings and its near endings.