An acclaimed Italian writer and activist was acquitted of incitement to damage property by a court in Turin on Monday, in what is considered a major victory for free speech advocates and critics of a controversial multibillion-euro high-speed rail line at the centre of the case.

Supporters of Erri De Luca broke into applause after judge Immacolata Iadeluca ruled that the 65-year-old Neapolitan writer was not guilty of incitement, bringing to an end a case that began in 2013, when De Luca said in two separate interviews that it was legitimate to sabotage the rail line between Italy and France known as the TAV.

The project is staunchly opposed by environmentalists and anti-globalisation activists in the No TAV movement, which now considers De Luca a hero. He has insisted since the start of the trial that his use of the word “sabotage” was misinterpreted because it does not always imply physical destruction , but that he would not alter his vocabulary to appease censors.

“An injustice has been prevented,” De Luca said shortly after the verdict was read. The court did not offer an explanation for the decision, except to say that the crime did not exist.

For the writer and his supporters, the case was significant not just because it put the TAV in the spotlight, but because of the seemingly heavy-handed decision to prosecute him and seek an eight-month jail term even though his comments did not provoke any immediate violence or damage to property. About 500 artists and writers, including Ken Loach and Salman Rushdie, signed a petition in support of the De Luca in a case that was seen as setting a dangerous precedent on free speech in Italy.

“If what I said is a crime, I will continue to say it and repeat it. The word sabotage has a noble meaning. It was also used by Mandela and Gandhi,” De Luca said in his final comments to the court before the judge began deliberations. He added that the TAV had been hindered by acts of legitimate sabotage in defence of people’s health, the soil, and the air of a community that was under threat.

The verdict was a blow to Italian prosecutors and Lyon Turin Ferroviaire, the French company building the line, who had argued that the writer’s comments represented a threat to the lives and safety of TAV employees.

They claimed De Luca was “instigating the commission of crimes and violations” that would hurt the company, its workers and the TAV construction site, which is considered an area of strategic national importance.

The project has been the subject of major and sometimes violent protests over the years, including arson attacks. Environmental groups claim the building of the TAV tunnel will release asbestos and other environmental toxins.

It is not just a local issue. The project has become a symbol across the country for waste and corporate greed, with many speculating that the 35-mile tunnel connecting Turin and Lyon will never be completed.

Supporters of the project say it will increase trade, lower transport costs and boost commuter services, so that one day a high-speed line might carry passengers from Lisbon to Kiev, and Rome to London.