The social media behemoth blocked the group’s account, which had around 250,000 followers, in September for violating the platform’s policy against spreading hate.
The far-right party has increased its following in Italy by leading anti-migrant campaigns on social media.
On Tuesday the judge ruled excluding the party from Facebook was “in contrast with the right to pluralism... eliminating or strongly compressing the possibility for association... to express its political messages”.
Facebook complied with the court order and restored the page in Italy, but the account remained inaccessible outside of the country.
A Facebook spokesperson said: “We have complied with the court order and restored the relevant Page and Profile. We are continuing to review the decision and are considering our options.”
The Roman court’s ruling made no reference to Instagram, which is owned by Facebook and also blocked the group’s account.
It had also said Facebook would be fined €800 (£668) for every day in violation of the judicial order.
It was unclear when Facebook restored the account and whether it incurred any fine.
“Magistrates order Facebook to reopen our pages, citing the constitution and stating that Casapound has the right to exist and to communicate on social media,” Casapound’s leader, Simone Di Stefano, wrote on Twitter.
Facebook also banned another neo-fascist group, Forza Nuova, in September. The page remains inaccessible.