The Strasbourg-based European Court of Human Rights awarded Arnaldo Cestaro 45,000 euros (USD 48,900) and said Italy must change its laws to criminalize torture.
The 2001 summit was marked by violent confrontations between black-clad protesters and police, and resulted in the first shooting death of an anti-globalization activist by police fire.
The night of July 21-22, Cestaro and a group of protesters were in a school housing the demonstrators when police stormed the building looking for members of the "black bloc" group of violent agitators.
The court ruled that Cestaro's treatment amounted to torture, and criticized the lack of accountability for those responsible. It found that Cestaro's torturers were never identified, much less punished, and that an Italian investigation resulted in officers being acquitted of the most serious charges because the statute of limitations had expired.
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The court's rulings are binding on the 47 member states of the Council of Europe, the continent's human rights watchdog, of which Italy is a member.
"We are now working in parliament to introduce it in the criminal code, with aggravating penalties" if a police officer is at fault, he told The Associated Press.
Nicolo' Paoletti, Cestaro's attorney, welcomed the ruling and the 45,000 euro damage award, but said the most important part of the ruling was that Italy must modify its legislation.