There were multiple court cases and this practice was found unlawful (and actually against EU law). But the government did not issue automatic refunds, and instead requested that people "actively appeal" with some time limits. They also refused to pay interest on the money withheld.
AFAIK, only about 50M Euro was paid back. A lot of funds gathered between 2002–2005 was never returned.
I've been living in Finland for 10+ years, and this whole story was super surprising for me to learn because the prevailing notion among people here is that Finland is the land of law, and everything is done correctly and legally, always, and we can and should trust the authorities.