The former political prisoner and Puerto Rican independence activist Oscar Lopez Rivera was released by Panamanian officials on Tuesday after being detained for 18 at the international airport while trying to travel to the conference, “America in Dispute” being held in Santa Cruz, Bolivia.

Lopez Rivera was held in custody by Panamanian airport authorities on his way to the Bolivian meeting despite carrying a valid passport.

Alejandro Molina, the spokesman for the political activist, said Lopez Rivera was arrested on the grounds that he was an ex-convict, and as such, Panamanian law allegedly prohibits him from traveling through the country.

Not until the Bolivian government intervened in the matter was Lopez Rivera freed.

The former political prisoner was finally freed in 2017 after then President Barack Obama commuted his sentence. The activist had been sentenced to 55 years in prison starting in 1981 for sedition. He was linked to the Armed Forces of National Liberation of Puerto Rico (FALN), an organization that fought for the independence of the Caribbean island.

The organizers of the seminary – Network of Intellectuals and Artists in Defense of Humanity – denounced Lopez Rivera’s detainment as unjust and with the intent to stop him for participating in the three day meeting in Bolivia.

The forum seeks to bring together intellectuals and left-wing thinkers to discuss and organize alternatives to neoliberal and imperialist aggression in the region.

Among the guest panelists are the Puerto Rican wrestler, personalities such as Argentine Atilio Boron, Venezuelan William Castillo and Bolivian government minister Carlos Romero.

Former Honduran President Manuel Zelaya, also on the list of forum attendees was also detained at the Honduran international airport, accused of not being vaccinated for yellow fever. The former head of state overthrown in a right-wing coup in 2009 defended that he was vaccinated.