Russia's Supreme Court upheld on Tuesday a ban on the ultra-right Movement Against Illegal Immigration (DPNI).
The Moscow City Court ordered DPNI's closure in April.
"This decision has given impetus to new ideas. We have new strength, and there'll be new projects and new organizations," DPNI leader Vladimir Yermolayev said outside the court.
DPNI - which tapped into rising nationalist sentiment in Russia - has called for curbs on the inflow of "incomers" and pushed for a law that would require immigrants to pass language and social communication tests.
Unofficial figures suggest there are between 4 and 5 million illegal immigrants in Russia, most of them from the ex-communist Central Asian republics.
Race riots in Moscow last year following the murder of a Russian football fan by a man from the North Caucasus have prompted the authorities to crack down on nationalist groups.
