Stasi can't be cops?

Having watched a program on the Discovery Channel the other day about the Stasi, the former East German state security ministry, I got interested and started looking up what information I could find, just for curiousity’s sake. at this site I ran across this nugget of information: After reunification, many former Stasi agents were prosecuted. Today, any former Stasi domestic espionage officer is barred from police work in Berlin.

My question is: why are former Stasi agents barred from police work? Is it because of fears that they would go about things as cops the way they used to as agents?

Time for my one and only Stasi joke:-

" Many former Stasi agents are now taxi drivers in Berlin.This is very useful because you only have to give your name and they already know where you live."