While Germany’s public museums are obliged to elucidate the origin of Nazi-looted art and to return these works to the heirs of the previous owners – even if they often resist this – there are no regulations for private collectors beyond the moral pressure to reach an agreement with the previous owners. If they bought the works in good faith, they are the rightful owners.
BGH ruling on Nazi-looted art: Collector must accept entry in Lost Art – Kultur
