Attorneys general from 22 states sued Tuesday to block President Donald Trump’s move to end a century-old immigration practice known as birthright citizenship guaranteeing that U.S.-born children are citizens regardless of their parents’ status.

Trump’s roughly 700-word executive order, issued late Monday, amounts to a fulfillment of something he’s talked about during the presidential campaign. But whether it succeeds is far from certain amid what is likely to be a lengthy legal battle over the president’s immigration policies and a constitutional right to citizenship.

The Democratic attorneys general and immigrant rights advocates say the question of birthright citizenship is settled law and that while presidents have broad authority, they are not kings.

“The president cannot, with a stroke of a pen, write the 14th Amendment out of existence, period,” New Jersey Attorney General Matt Platkin said.

The White House said it’s ready to face the states in court and called the lawsuits “nothing more than an extension of the Left’s resistance.”

“Radical Leftists can either choose to swim against the tide and reject the overwhelming will of the people, or they can get on board and work with President Trump,” White House deputy press secretary Harrison Fields said.

Connecticut Attorney General William Tong, a U.S. citizen by birthright and the nation’s first Chinese American elected attorney general, said the lawsuit was personal for him.

“The 14th Amendment says what it means, and it means what it says —- if you are born on American soil, you are an American. Period. Full stop,” he said.

“There is no legitimate legal debate on this question. But the fact that Trump is dead wrong will not prevent him from inflicting serious harm right now on American families like my own.”