Critics argue that the proposed agreement would threaten Iranian dissidents.
ADVERTISEMENTBelgium's Constitutional Court has suspended a controversial prisoner swap treaty with Iran amid pressure from activists.
The agreement to mutually transfer convicted criminals was approved by Belgium's parliament over the summer, but the court has ruled that the treaty posed "a risk of serious and difficult-to-repair harm" to Iranian opponents.
Exiled Iranians and NGOs have slammed the proposed deal as "shameful" and say it would allow Iran to engage in "hostage diplomacy".
Critics had also argued that the deal would let convicted Iranian terrorist Assadollah Assadi be exchanged and pardoned.
The former diplomat is currently serving a 20-year prison sentence in Belgium for plotting to bomb a gathering of Iranian opponents near Paris in June 2018. Tehran has rejected allegations that Assadi was operating under the instructions of Iranian intelligence and has called for his "unconditional release".
"There is no longer any legal basis for this transfer," lawyer François Tulkens told the Belgian court.
The decision to suspend the treaty has been praised by Iranian dissidents. Judges will have to rule on censuring the treaty in the next three months.
Belgian Justice Minister Vincent Van Quickenborne has defended the agreement while acknowledging the need to protect innocent people from Iran's "authoritarian" regime.
The deal could have allowed Iran to free Belgian humanitarian worker Olivier Vandecasteele, who has been held "illegally" in Tehran on espionage charges since February.
The 41-year-old has reportedly been sentenced to 28 years in prison
Another detainee in Iran -- Swedish-Iranian academic Ahmadreza Djalali -- has taught in Belgium and is facing the death penalty.