It's Eritrean mining law. You must have missed this part when reading the Annual Report.
"...on application for a mining license, the Eritrean government is entitled to a 10% free-carried interest. The government also, after delivery of a Bankable Feasibility Study (BFS) has the right to purchase on negotiated terms an additional 30% equity participation interest in any mining project and a 3.5% royalty on potash salts."
