ICAO can't mandate anything. Each nation is sovereign. There is no higher authority that can mandate compliance.
Actually they can and that’s why the Council decides and the General Assembly passes it. If everyone in the council agrees to it.
The issue to me is the VFR. It’s crazy to have VFR in such a congested controlled airspace. I know it’s state aircraft but in many countries I know in such a class controlled airspace they need to have ads-b and fly IFR. Am I correct in saying that there was more than one CRJ in the area?