The ruling was a major blow to the conservative government’s plan to have asylum claims heard in Albania instead of Italy.

Italian judges on Friday struck down a request by the government to hold a group of migrants in a detention center in Albania, ordering that they should be taken to Italy, in a major setback for Giorgia Meloni’s flagship policy of outsourcing asylum requests.

It was the first ruling on the new policy since Ms. Meloni’s right-wing government began carrying out the plan, with the Italian Navy this week bringing a group of migrants to a center built in Albania to hear asylum claims from refugees who had been bound for Italy.

The judges’ decision, which for now applied to only 12 migrants, could likely apply to others, casting doubt on the future of an approach that other nations, and even the European Commission’s president, were looking to as a model. Italy’s interior minister, Matteo Piantedosi, said the government would appeal the judges’ decision and that it was ready to take the case all the way to Italy’s highest court.

Under the plan, Italy is seeking to send migrants rescued in the Mediterranean by Italian ships to the Balkan nation, where their asylum claims would be assessed. Only “non-vulnerable” men coming from “safe countries” were to be taken to the centers there. (Italy considers vulnerable men to be those who are ill and disabled. Both Egypt and Bangladesh are categorized as safe, according to Italian law.)