Olivier Vandecasteele has been imprisoned since February last year.
ADVERTISEMENTBelgium's constitutional court ruled on Friday that a contentious prisoner transfer treaty with Iran is legal, paving the way for the release of jailed Belgian aid worker, Olivier Vandecasteele.
The deal, agreed in July, between Brussels and Tehran was suspended by the Court last year, after opponents of the Iranian regime living abroad appealed against its legality, fearing an Iranian diplomat called Assadollah Assadi - convicted of terrorism in Belgium - would escape punishment in Iran.
Olivier Vandecasteele was supposed to be involved in a prisoner swap with Assadi, after he was imprisoned in Tehran last February on trumped-up charges of espionage and sentenced to 40 years in jail with 74 lashes, but has so far remained in prison.
The ruling means that the jailed Belgian could soon be freed, but the Court did leave one major hiccup in place.
Any decision by the government to go ahead with a prisoner transfer would mean it would have to notify the victims of the convicted person, in this instance the Iranians living abroad involved in the original Assadi terrorism case, who can ask for a review of the decision in the court of first instance.
It means that any possible swap involving Vandecasteele and the convicted Iranian terrorist would be subject to a legal analysis.
A statement from the office of Belgian Prime Minister Alexander De Croo said that they are happy with the Court's decision.
"This decision on its merits, confirms the fact that this transfer treaty meets all the rules of international law," the Prime Minister's Office said.
"The government has always considered that this treaty was an important legal instrument to allow the return of Olivier Vandecasteele to our country. The government will resolutely continue its efforts in this direction.
"To achieve this goal, we are in close and continuous contact with the family of Olivier Vandecasteele. The necessary steps will now be taken to finalise the treaty, taking into account the judgment of the Constitutional Court."
Philippe Hensmans the director of Amnesty International Belgium has welcomed the possible release of Vandecasteele, but is against any prisoner swap on the basis that Assadi would more than likely go free in Iran and could pose a danger in the future.
"It is a difficult decision to make and there is no clear way to do it, but sending Assadi back makes it possible for other people, for this situation, to happen again and again," Hensmans told Euronews.
"Assadi was planning to kill a lot of people. He had 500 grams of explosives ready to use in a football stadium, so that was extremely dangerous."
The Amnesty director added that he does not know what the alternatives are to a prisoner swap, but Belgium must figure it out.
"The Belgium government has to take all the necessary measures and try to find a solution. If they do the exchange, indeed that's a way of reinforcing the Iranian policy [of Western prisoner-taking]," he said.
"I wouldn't like to be the Prime Minister today because these are extremely difficult decisions to be taken, but on the other hand, it is a question of balance. There is no reason to leave Vandecasteele in jail, but there must be other solutions than exchanging with this prisoner [Assadi]."