In a statement released Wednesday, California Senate President Kevin de Leon and Assembly Speaker Anthony Rendon -- both Democrats -- announced they had "hired outside legal counsel to advise on potential legal challenges with the incoming Trump administration."
"With the upcoming change in administrations, we expect that there will be extraordinary challenges for California in the uncertain times ahead," the state leaders said. They vowed to protect "California's economy and our sensible policies on climate change, health care, civil rights, and immigration."
To accomplish that goal, the legislature said it retained the Covington & Burling law firm, led by Holder.
"Mr. Holder and his team will serve as outside legal counsel to the Legislature, advising us in our efforts to resist any attempts to roll back the progress California has made."
CNN has reached out to the Trump transition team for comment and have not yet received a response.
In the statement, Holder said that he was "honored" that his legal firm had been tapped by the California legislature, and said he is "confident that our expertise across a wide array of federal legal and regulatory issues will be a great resource."
The California legislature's move to hire Holder, a high-profile Obama alum, adds to the deep-blue state's reputation as the center of liberal opposition
to the new Trump administration.
"This is a critical moment in the history of our nation. We have an obligation to defend the people who elected us and the policies and diversity that make California an example of what truly makes our nation great," the state's Democratic leaders said.
State Democratic leaders have promised to fight to maintain "sanctuary cities
" -- something Trump pledged to fight during his presidential campaign -- and De Leon, with Rendon, introduced sweeping state legislation in late December to blunt Trump's expected immigration policies. The measures, expected to pass early this year, would offer undocumented immigrants more access to legal help and would further spell out the limits of local law enforcement's cooperation with federal immigration agents.
De León, California's first Latino elected leader of the state Senate in more than a century, has been signaling his willingness to fight Republicans since Trump was elected.
"We don't want to fight," he said in December. "We're not looking for a fight. But if necessary, we will fight to protect the values of California. Given what I've seen so far with regard to the Cabinet selections, there probably is going to be a fight around the corner very, very soon."