Attorneys general from 22 states have sued to block President Donald Trump’s move to end a century-old immigration policy known as birthright citizenship guaranteeing that U.S.

“Protecting the Meaning and Value of American Citizenship”—better known as the birthright citizenship executive order —attempts to cancel the 14th Amendment to the US Constitution. Getting rid of constitutional amendments via executive order is new, and, for me at least, “the worst.”

One of the many executive orders President Donald Trump signed on Monday included one to end birthright citizenship. Here's what to know about it and why lawsuits have already been filed.