The US Department of Transportation (DOT) sent a letter notifying Kuwait Airways that it violated U.S. anti-discrimination law when it refused to sell a ticket from New York to London to an Israeli passport holder.

Jewish advocacy group the Anti-Defamation League (ADL) today welcomed the move.

ADL called the notification “a clear warning” to other airlines flying into the United States who still comply with an Arab boycott of Israel. The DOT launched an investigation of the incident following a complaint by an Israeli citizen, Eldad Gatt, who tried to buy the ticket in 2013. In a letter to the airline, the DOT said that Kuwait Airways “availed itself of the facilities and benefits of the U.S and must comply with its laws.”

“With this decision, the U.S. government is sending a clear and appropriate warning that those who wish to uphold the Arab boycott of Israel and discriminate against Israelis are acting in violation of American law and risk losing access to U.S. facilities unless they comply,” said Jonathan A. Greenblatt, ADL National Director. “We commend Secretary Foxx and the Department for this just and correct action, and express our appreciation to Senator Schumer and others who have raised this issue.”