Europes restrictions on coins.

Why is it illegal in some places in Europe to poses World War 2 German coins?

You would have to ask a more specific question to get a more specific answer (which places and in what context). But it probably has something to do with that fact they're covered in symbols from a genocidal regime that tried to conquer the entire continent and many people frown on such behavior.

You should also provide proof that and if where these restriction should exist I know of no "place" where the possession is illegal.
There are some restriction of selling them openly because of the symbolisms but you can never the less buy and sell them easily (at least I never had any problems).

As a matter of fact, I'm planning to visit the weekly antiques market in Tongeren (Belgium) and stumbled on the regulations for merchants: while it is forbidden to offer Nazi materials for sale, an explicit exception is made for coins from that era.
Coins with swastika symbols are easy to come by in Europe, and nobody makes a big problem of that. But I've also never seen people with questionable convictions flash their 3rd Reich pfennigs. Perhaps that's why.