Egyptian President Abdel Fattah El-Sisi ratified a treaty that hands over two strategic islands in the Red Sea to Saudi Arabia, despite protests about the move in Egypt.

The deal to hand over the two islands of Tiran and Sanafir was reached in 2016 after a visit to Egypt by Saudi Arabia’s King Salman. Yet the deal has faced widespread opposition and legal challenges by opponents who accuse El-Sisi of selling out the country for Saudi money. Nevertheless, the deal was approved by Egypt’s parliament and was signed Saturday by El-Sisi.

The uninhabited islands that sit on the southern entry to the Gulf of Aqaba were originally given to Egypt in 1950 by Saudi Arabia, in order to protect them from Israel. Later, the islands played an important role in setting off the 1967 Six-Day War when Egypt closed the Straits of Tiran to Israeli ships, preventing Israeli access to the Red Sea and Indian Ocean.

United Nations peacekeepers maintain a presence on Tiran Island as part of the 1979 Israel-Egypt peace treaty. Under the treaty’s terms, Israel gave its approval for the Egyptian-Saudi agreement as long as the Saudis maintained the treaty’s clauses pertaining to Israeli shipping through the Straits of Tiran.