A court in Finland has refused to extradite a Russian nationalist fighter to Ukraine and ruled to release him from detention, Finnish mediareported Friday.Since 2016, Ukrainian authorities have sought the arrest of Yan Petrovsky, a Russian-Norwegian national, on terrorism charges, accusing him of assisting pro-Russian rebels in eastern Ukraine as a member of the far-right group Rusich in 2014-15.Finnish border agents detained Petrovsky at Helsinki Airport in July as he bordered a flight to France, charging him with violating immigration rules.Petrovsky, who is under Western sanctions, wasreportedly able to cross into Finland with his wife and three children after changing his identity documents under the new name of Voislav Torden.Finland’s Supreme Court cited “conditions in Ukrainian prisons” for its refusal to hand Petrovsky over to Ukraine, according to the Finnish newspaper Helsingin Sanomat.The court ordered Petrovsky’s immediate release in a decision his lawyer Heikki Lampela described as a “victory.”Petrovsky is described as the co-founder of Rusich, which is believed to have fought on the side of pro-Russian separatists in eastern Ukraine since 2014, as well as alongside Russian troops in Moscow's invasion of Ukraine.Rusich members regularlydisplay far-right symbols and have beenaccused of war crimes in Ukraine.