After failing to receive billions of dollars from Congress to fund his border wall, President Donald Trump declared a national emergency on Friday. “We’re going to confront the national security crisis in our southern border, and we’re going to do it one way or the other,” he said in a televised statement. “It’s an invasion. We have an invasion of drugs and criminals coming into our country.” Not only have many experts and politicians denounced his comments – there is no security crisis along the US-Mexico border – now 16 states, led by Californa Attorney General Xavier Becerra, have filed a lawsuit challenging Trump.

In a interview with CNN on Monday, Becerra said, “We’re going to try to halt the President from violating the Constitution, the separation of powers, from stealing money from Americans and states that has been allocated by Congress, lawfully.”

In another interview, with ABC’s This Week, the AG revealed that California and other states – Colorado, Connecticut, Delaware, Hawaii, Illinois, Maine, Maryland, Michigan, Minnesota, Nevada, New Jersey, New Mexico, New York, Oregon, and Virginia – were ready because they knew “something like this might happen.” And though Trump has focused on Texas and the border wall (and not California’s border), Becerra said he feels confident he can prove that the border wall brings harm.

“We’re confident there are at least eight billion ways that we can prove harm,” he said on This Week on Sunday. “And once we are all clear, all the different states are clear, what pots of money that taxpayers sent to DC, he going to raid, which Congress dedicated to different types of services; whether it’s emergency services, or whether it’s fires of mudslides in California, or maybe tornadoes and floods in other parts of the country, or whether it’s our military men and women and their families who live on military installations that might, that might have money taken away from them, or whether it’s money taken away from drug interdiction efforts in places like California, a number of states, and certainly Americans, will be harmed. And we’re all going to be prepared.”

This lawsuit is not the only hurdle for the Trump Administration. The Center for Biological Diversity, Border Network for Human Rights, and the American Civil Liberties Union have also filed lawsuits. Additionally, there’s a chance that a joint resolution from House Democrats could end the declaration (though this requires cooperation from the House of Representatives and the Senate before it ends up on Trump’s desk).