Hmmm, I am not sure about the 10-year rule. When I received my Karta Stałego Pobytu 4 years ago, the friendly staff at the EU section in Długa 5 told me I was entitled to apply for Polish citizenship - I was living 5 years in Poland at that time. So.... Maybe the conditions have been tightened?
Anyway I was not interested, as it does not give me anything extra, Poland being in the EU.
It's important that the legal basis for him being in PL has remained the same for 10 years
What do you mean with that, Jon ?
Easily enough in the same way that cleaning King Augeas' stables was easy enough (just a bit smelly and would take a while)?
Harry is still traumatized by the white A4 piece of paper they gave him instead of a proper Karta Pobytu :)