In a ruling greeted with fury by relatives of the victims, the Court of Cassation on Wednesday quashed the conviction and 18-year prison sentence given to tycoon Stephan Schmidheiny over inadequate safety provisions in asbestos-cement plants run by his now defunct group Eternit in Italy in the 1970s and 80s.
"If an episode like Eternit is not a crime or if it is a crime and subject to prescription then we have to change the rules of the game," Renzi said.
"We cannot have this nightmare of prescription. The demand for justice does not diminish with time. There is some pain that cannot be healed by time."
The court ruled that Schmidheiny, a scion of a Swiss industrial dynasty now regarded as a philanthrophist, should not have been convicted of causing a health or environmental catastrophe because the verdict came more than 12 years after the crime and was therefore subject to the statute of limitation applicable to the specific charges.
Raffaele Guariniello, the Turin prosecutor in charge of the case, said he would seek to have Schmidheiny retried for homicide.
"The Court of Cassation did not conclude in favour of absolution," he said. "The crime was committed, and it was committed with intent.
"This is not a moment of disappointment, it is a new start. We will not throw in the towel."
Three separate homicide cases have been opened in Turin, one related to Italian deaths from mesothelioma, a form of lung cancer, one related to the deaths of ex-workers at an asbestos mine near Turin and one into the deaths of Italians who worked in Eternit plants in Switzerland and Brazil.
The pursuit of Schmidheiny was the biggest case of its kind against a multinational over asbestos-related deaths.
After a criminal probe launched in 2004, the Swiss tycoon was first convicted, after a three-year trial, in 2012 and sentenced in absentia to 16 years in prison. That term was raised to 18 years by an appeal court a year later.
Asbestos-related conditions have decimated whole families. Romana Blassotti, 85, who lost her husband, daughter, sister and two other close relatives, said the latest court ruling was hard to bear.
"I am tired of seeing people die around me. This hurts like you cannot imagine," she said.
"But we will keep fighting, not for us but for our young people," the pensioner told La Repubblica.
The two lower courts both concluded that Eternit had continued to use asbestos with a negligent disregard for safety up until its bankruptcy in 1986, by which time the fatal toxicity of the material was widely recognized, not just by industry or health specialists, who first warned of its dangers a century ago.
Schmidheiny was once referred to by Forbes as the "Bill Gates of Switzerland" for his philanthropy. The US magazine estimates his personal fortune at $3 billion (€2.4 billion).
His lawyers argued in the first two trials that he should not have been prosecuted as he did not have direct involvement in Eternit Italy.
The legal point was also discussed in the lower courts, where judges ruled that the date of the crime was elastic since the health problems it caused were still emerging.
Once hailed as a miracle product, asbestos was used mainly as building insulation for its sound absorption and resistance to fire, heat and electrical damage. It was banned in Europe in 2005, but is still widely used in the developing world.
The inhalation of asbestos fibres can cause lung inflammation and cancer, and symptoms can take up to 20 years to manifest after exposure.