Because:
1) the first time idiotic commies decided to put it on a referendum honestly thinking the people will pass it and "force" the government to implement it in law
2) the second time it was the other way around, euroliberal opposition decided to block law the government already passed on a referendum which rejected the law, and the communist government asked the court
3) then the court took 7 years to process it lol. also presumably they waited 2 years for Janša government to be finally deposed by incessant communist media shilling so that the commies are back in power when the decision is published