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, wasre…