İsmail Beheşti was on his way to check on his ship, the Conscience, at the Port of Istanbul. It was the end of August, and he hoped the 220-foot passenger yacht would soon be loaded with aid and volunteers, sailing for Gaza to break Israel’s illegal blockade. But as he entered the port, where the ship had been moored for months, he was physically stopped.

“The security forces did not allow me to enter the port. They kicked me out by force,” recalled Beheşti. To his great surprise, he said, the security officers told him “‘No, you are on the blacklist. We will not let you go and see your ship.’”

It was the latest roadblock for Beheşti and his fellow activists from an international coalition that has been trying since April to deliver humanitarian aid to Gaza. They had already struggled to find countries that would lend their flags to the ships in the flotilla, as such a move could be seen as antagonistic to Israel. Once they did obtain flags, the flotilla planned to depart from Turkey, which famously supported a 2010 effort to break Israel’s siege of Gaza. But now, even though the Conscience has secured a flag and the support of U.N. rapporteurs, Turkish authorities are continually blocking its departure.