RFE/RL's Ukrainian Service reports.
Alla Aleksandrovska, first secretary of the Ukrainian Communist Party's Kharkiv Oblast Committee, said on February 22 that the Communists and their lawyers were collecting all the documents needed to file a lawsuit against that day's unveiling of the plaque for Josyf.
Slipyj is a prominent dissident who led the Ukrainian Greek Catholic Church during the Soviet era and was viciously persecuted by authorities. He spent many years in Soviet labor camps and jails.
Responding to pressure from the Vatican and U.S. President John F. Kennedy, the Soviet leadership allowed Patriarch Josyf to leave the USSR in 1963. He died in Rome in 1984 at the age of 92.
Slipyj was made a cardinal by Pope Paul VI in 1965. He was also the major archbishop of Lviv as head of the Ukrainian Greek Catholic Church in 1944-84.
The first plaque commemorating Patriarch Slipyj was unveiled in Kharkiv in 2005. Pro-Russian groups damaged the plaque in 2008 and the local Catholic congregation and the organization of Ukrainian Youth tried to restore the plaque.
In 2010, pro-Russian organizations in Kharkiv filed a lawsuit against plans for the plaque and won their case. The leader of the Great Rus organization, Yury Apukhtin and his supporters, then destroyed the plaque.
About 8 percent of Ukraine's Christians belong to the Ukrainian Greek Catholic Church.