... and everybody who uses a different software not approved by state will be flagged as a criminal. This will make the job of police and spooks easier, we know there was order and security in East Germany or other countries of the Soviet block.

Now consider the cost of such 'solution'. Free speech gets redefined, most of the people get divided into informants,opportunists, naive state suckers and silent fragmented opposition. Is that kind of security and police state an acceptable cost? For preventing small number of violent deaths each year?

There are much bigger problems in Western societies than a bunch of lunatics killing small number of people, but those can't be used so easily to make a power grab.

How do you ensure that what was the reviewed source is what is actually being used? Also, how do you encode in source code who is the correct target to use this against, for now and in the future?

That's a perfect solution actually. But sadly, we aren't there just yet. There are nuances with these things that software can't (yet) pickup.

So humans have to do it till then. We were maybe born too early. But I think it makes things interesting.

That means there are still problems for you and me to solve.