The Belgian Parliament has ratified a controversial prisoner swap treaty with Iran, which facilitates repatriating an Iranian diplomat sentenced to 20 years in jail on a terrorism conviction.

Following several postponements of the vote and a heated debate Wednesday, out of the 131 lawmakers present, 79 voted in favor while 41 rejected the treaty, and 11 abstained just after midnight. 

Critics fear that the treaty, which would permit Iranians convicted in Belgium to serve their sentences in Iran and vice versa, will pave the way for the release of Assadollah Assadi, a terrorist convicted for his role in a plot to bomb a gathering of Albania-based opposition group, Mujahedin-e Khalq Organization (MEK) organization in Paris four years ago.

Several Belgian lawmakers shared concerns about why the treaty was rushed through parliament before the summer break, and said they were not able to consult enough external experts ahead of the vote.

Samuel Cogolati, a Green MP, said, “We had to be able to publicly express our reservations and deep concerns, and at the same time do our job as parliamentarians. We tried as much as possible to consolidate, to give guarantees for the rule of law, while ensuring the release of our Belgian compatriot in Iran.”

Meanwhile, Tehran has been holding Belgian humanitarian worker, Olivier Vandecasteele, in jail since February as leverage.

Belgium’s Justice Minister Vincent Van Quickenborne said on July the 6 that the assessment of the Belgian security service was that the failure to pass the bill would increase security threats.