California officials said Wednesday that they’re prepared to fight President Donald Trump over his announcement that he’s revoking the state’s legal authority to set its own car emissions standards.

At a press conference, state leaders emphasized that they’ve long anticipated this move by the Trump administration and that they plan to take Trump to court over it as soon as possible.

“This is the fight of a lifetime for us. We have to win this,” California Air Resources Board chairwoman Mary Nichols said, adding that she’s been paying her dues to the State Bar of California “just in readiness for this moment,” so that she could be part of the litigation.

Shortly before she spoke, Trump tweeted out confirmation that he was revoking a waiver that’s long allowed the state to establish its own tailpipe emissions policy, upending decades of bipartisan support for that exception.