"He was immediately taken to the immigration holding centre at KLIA," Gabriel told Malaysiakini.
Following some negotiations, she was eventually allowed to do so.
He said those beneficiaries and kickbacks from the RM7.3 billion Scorpene submarine deal would be exposed when the matter is raised at the French corruption trial against defence giant DCNS.
"We touched down at 11.40am from Penang, and immediately three immigration officers entered the plane and detained him. There was also another officer in a green uniform, who I believe to be with the auxiliary police.
"They then took him to the immigration holding centre, but they stopped me from entering. They were shouting 'jangan ikut, jangan ikut' while holding up their hands," she said.
Gabriel slammed the authorities for taking such "arbitrary and irrational" action in detaining Bourdon while he was still on the plane, calling it a hallmark of a government "moving towards a full dictatorship".
Fadiah Nadwa Fitri of Lawyers for Liberty pointed out that it would be very difficult to challenge Bourdon's detention, even if the authorities did not give any grounds for it, as the Immigration Act allowed them far-reaching powers to act.
"Under the Act, they have the power to stop him, deny him entry and deport him with no obligation to explain why.
"But where is the due process? If you infringe someone's right to freedom of movement, then at least tell them why," Fadiah said.
She explained that Bourdon's detention was based on Section 9(a) of the Immigration Act, which gives the director-general powers to prohibit entry and cancel permits of individuals considered prejudicial to the nation, "where he deems to be expedient to do so".
"What is so prejudicial to Bourdon being here? That is the question (Prime Minister) Najib (Abdul Razak) should answer," Fadiah said.
Gabriel echoed Fadiah's sentiments, pointing out that the government's action against Bourdon, who was scheduled to fly home on Sunday, would only raise more questions surrounding the controversial submarine deal.
"Why is the government so afraid? This incident only shows that the government really does have something to hide," she said.
Meanwhile, Suaram project coordinator Sarah Devaraj said their fund-raising dinner in Petaling Jaya tonight will go on as scheduled, despite the absence of Bourdon.
She said they expected at least 700 people to attend the event at the PJ Civic Centre, aimed at raising funds to cover the legal costs of Suaram's court action in France.
Such payments are illegal under French laws. Perimekar is a subsidiary of KS Ombak Laut Sdn Bhd, of which the major shareholder is Abdul Razak's wife, Mazlinda Makhzan (right).
Bourdon has uncovered another 30 million euros (RM150 million) paid to DCNS' commercial network Thales and another 2.5 million euros (RM7.5 million) to an unknown recipient.
Suaram recently revealed that a third commission, an amount bigger than the earlier two, had been paid to highly placed government officials.
Bourdon and his team of lawyers at Sherpa - a not-for-profit organisation he founded in 2001 that focuses on improving legal tools to promote corporate social responsibility - have been providing pro bono services to Suaram thus far.
Active in initiating legal procedures in France against former Serbian and Rwandan leaders suspected of crimes against humanity and war crimes, Bourdon also served as legal council for Franco-Chilean families who were victims of the former dictator Augusto Pinochet.
From 1995 to 2000, he was general-secretary of the International Federation for Human Rights (IFHR).