Fifteen states and the District of Columbia have filed a lawsuit in New York challenging President Donald Trump’s plan to end a program protecting young immigrants from deportation.

The suit was first announced by Washington state Attorney General Bob Ferguson, who called Trump’s act “a dark time for our country.”

Plaintiffs include New York, Massachusetts, Washington, Connecticut, Delaware, District of Columbia, Hawaii, Illinois, Iowa, New Mexico, North Carolina, Oregon, Pennsylvania, Rhode Island, Vermont and Virginia

On Tuesday, U.S. Attorney General Jeff Sessions said the program, known as the Deferred Action for Childhood Arrivals or DACA, will end in six months to give Congress time to find a legislative solution for the immigrants.

The participants were brought to the U.S. illegally as children or came with families who overstayed visas.