Due to a hint of a reader (thank you!) I noticed, that Croatian Government published a modification of the Seaports Act. The new added Article 76a of this document (published in the Narodne Novine, see here) says:
"In the waters nearby a Nautical Anchorage, and at distances up to 300 m from the Nautical Anchorage in the direction of the open sea anchoring is prohibited with own anchoring system, except in cases of force majeure or distress at sea."
As far as I understand, this means that from now on anchoring with your own anchor is forbidden 300 meters around the Concession Area. Good news for concessionaires but bad news for croatian sailing tourism...