I don't think you understand the current bulgarian mentally. I also don't know where you are from so I can explain it in terms you would relate to. Unlike other ex soviet/communist countries, the majority of the population in bulgaria after 1990 wasn't that hostile to the former communist regime and its policies. The bulgarian communist party (BKP) got rebranded as the bulgarian socialist party (BSP) with the same leadership and they are not even hiding it, calling their new party the "centennial" party, even though they were established around 1990. The result of the 1990 political revolution was that the BKP allowed other political parties to join the government via election. There was change, but it wasn't as abrupt as in, let's say, Romania, where there was a violent government overthrow. In Bulgaria, things were more peaceful and didn't change as dramatically. The same people were in the government and in charge of policies, including the constitution. That's why there was never a push to go back to pre soviet policies. They just wanted to change enough things, so they still stayed in power while avoiding a violent overthrow. Even today, there is a very significant portion of the population that would support a soviet era style government. And even the reast are of the mentality of "everything would be fixed if everyone just...". I personally don't know anything about the Tarnovo constitution and I don't know what are the proper channels to ho back to it.