File Photo: Migrants arrive in the harbour of the Italian island of Lampedusa. AFP
The case was brought by Eritreans detained along with dozens of other migrants on the Diciotti military ship after Salvini -- who heads an anti-immigration party -- refused permission to disembark in an Italian port while he tried to get other European states to take them.
The Court of Cassation ruled Thursday that Rome must pay compensation and instructed another court to determine the sum.
The judges found "the obligation to rescue at sea... is a duty" imposed on everyone and prevails over measures "intended to combat illegal immigration".
Prime Minister Giorgia Meloni, who has made stopping the arrival of migrant boats from North Africa one of her key battles, defended Salvini, who is now deputy prime minister in her right-wing coalition.
"The government will have to compensate, with the money of honest Italian citizens who pay taxes, people who tried to enter Italy illegally," she wrote on X.
Meloni's government frequently clashes with judges it deems "politicised", and she said it was "frustrating" to have to fork out money for compensation "while we do not have enough resources to do everything that needs doing".
Speaking to reporters in Milan, Salvini said that "if some judges love illegal migrants so much, they should take them into their homes and maintain them."
The ruling also sparked an angry reaction from Salvini's League party, which slammed it as "absurd".
"Let these judges pay out of their own pockets if they love illegal immigrants so much," it said in a statement.
Salvini was acquitted in December in a trial relating to a similar case in which he was accused of kidnap for blocking migrants at sea in 2019.
Prosecutors had sought to try Salvini in the 2018 Diciotti case as well, but on that occasion parliament voted against stripping him of his immunity.
Meloni's government has adopted a tough stance against the tens of thousands of migrants who each year attempt the perilous Mediterranean crossing to Italy in rickety boats in a bid to enter Europe.
However, just over 7,000 migrants have landed in Italy since the start of the year, compared to 4,895 during the same period in 2024, according to interior ministry data.
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