The reconciliation law was approved on Wednesday by 117 deputies to nine after a night of angry debate, which led the opposition to walkout of parliament and accuse the ruling coalition of acting like a mafia.
Government supporters accused them of playing to the gallery.
"We're facing some of the most simplistic populism I've ever seen," Samir Labidi, a representative of the ruling Nidaa Tounes party in Tunis told RFI.
President Beji Caid Essebsi's ruling party has been pushing the reconciliation law since 2015, arguing it will improve the investment climate and help revive Tunisia's ailing economy.
"I don't understand what all the fuss is about," says Labidi, arguing that it fills a legal loophole in Tunisia's 2013 Transitional Justice Law.
That aimed to bring past abusers to account for their crimes and included a provision to pardon corrupt businesspeople if they fully complied with the transitional justice process and repaid their ill-gotten gains.
This law was "a legal absurdity", Labidi maintains. "For the civil servant who never stole, this law lets them fall through the cracks. The reconciliation law fills this legal loophole."
NGOs fear threat to Arab Spring's gains
But many civil society leaders fear the law will whitewash the entrenched corruption that fuelled the public anger behind the 2011 Arab Spring.
"This reconciliation bill is a set back to freedom and liberty in Tunisia," Amine Allouche, a member of parliamentary watchdog Bawsala told RFI.
"It offers amnesty, it doesn't offer reconciliation. It offers amnesty to corrupt civil servants and the like, meaning their ministers and high officials who served under the Ben Ali regime and who were involved in administrative fraud that led in many cases to financial fraud and to economic fraud."
Faced with widespread resistance when the law was first proposed two years ago, the government has had to amend it to exclude businessmen from the amnesty proposal.
In the final version, pardons will only be granted to those who followed orders from corrupt leaders but did not benefit personally, essentially just public officials.
Who is corrupt?
Yet determining who was corrupt and who wasn't is likely to prove a challenge in itself.
"The short answer is it probably won't answer that question," says Monica Marks, a Tunisia expert at Oxford University.
"They were all working for the corrupt dictator Ben Ali. So they could potentially all argue that they were simply taking orders and that they were all victims of a corrupt judicial system. So how is it possible to hold anyone to account?"
And that's the worry. Critics like Marks say the current law will infringe the transitional justice process that is already underway.
"The transitional justice law was a victim-centred process whose end goal was justice," Marks told RFI.
"The reconciliation law was proposed with the explicit goal of undermining the transitional justice law and setting up a parallel mechanism whose end goal was amnesty for the corrupt."
Many Tunisians have questioned the government's motives for prioritising this law over legislation they believe is more urgent.
So a law that declares it wants reconciliation may have had the opposite effect.