http://www.theguardian.com/world/2016/apr/15/angela-merkel-a...
But it’s also just an ancient law …
How ancient can these laws be? The BRD is not that old.
Basically it's a holdover from the monarchy, and there are similar rules across much of europe for the same reason. It seems interesting that these laws hang on despite the massive changes to borders and governments in europe since the 1800's
Courts do not prosecute people. They decide cases. The government (that is, the elected part) prosecutes people, at least in many cases. The prosecutor is either appointed by an elected official or elected directly. Therefore it is up to an elected official, either directly or indirectly, to decide whether or not to prosecute a case.