Ukraine's ultranationalist Svoboda (Freedom) party has said it would call mass rallies if Stepan Bandera is stripped of his title as a national hero.
Former President Viktor Yushchenko, known for his promotion of Ukrainian nationalism, issued a controversial decree in January to award one-time Nazi collaborator Bandera the title of a national hero about a month before his presidential term expired in February.
Bandera was a leader of Ukrainian nationalists who fought for the independence of Ukraine against Poland and the Soviet Union during WWII and collaborated with the Nazis.
The decree honoring Bandera has provoked anger from both Russia and the West. Late Polish President Lech Kaczynski said the order ran contrary to the historical truth.
A Donetsk-based lawyer later appealed the decree in a local court on the grounds that the national hero status can only be conferred to Ukrainian nationals, which Bandera was not as Ukraine became an independent state only in 1991.
A Donetsk court pronounced on Wednesday illegal a decree issued by Yushchenko in October 2007 to award the Hero of Ukraine title to another leader of Ukrainian nationalists, Roman Shukhevych, on the same grounds.
Both decrees issued by Yushchenko can only be repealed by the country's new leader, President Viktor Yanukovych, who is seen as more a pro-Russian politician than Yushchenko.
The party said in a message published on its website on Thursday, that it calls for "each Ukrainian citizen, who appreciates his pride and dignity, to participate in mass public protests against the new authorities" if the decrees are scrapped.
The Svoboda party members also intend to appeal the court's ruling on Shukhevych.
KIEV, April 22 (RIA Novosti)