That revving you hear from Sacramento is the sound of California’s Democratic leaders preparing to sue the tar out of the Trump administration.

We’ve seen this all before.

California sued the Trump administration 123 times between 2017 and 2021, according to Attorney General Rob Bonta’s office. It spent about $10 million a year in doing so. A majority of the lawsuits dealt with environment rules, immigration, and health care.

Legal and policy experts expect those same issues to take center stage during Trump 2.0.

That’s why Bonta’s team started to prepare legal briefs months ahead of the election, it’s why Gov. Gavin Newsom called for a special legislative session to “Trump-proof” California, and it’s why state Democrats have agreed to allocate $50 million to fight Trump in court — a move that state Republicans denounced as a “slush fund” for “hypothetical fights.”

Trump lost more than two-thirds of the lawsuits filed against his rules in his first term. His win rate of 31% was lower than that of the three administrations prior, according to an analysis by the Institute of Policy Integrity at the New York University School of Law.

What do California’s past legal skirmishes with the Trump administration 1.0 tell us about the policy battles to come? And how might this time be different?

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Will Trump Be More Strategic?

Many experts say the new Trump administration could be more strategic and wise this time. In his first round, his policy proposals were often rushed through and failed to pass legal muster.

“That’s something we are certainly worried about this second time around, that they’ll make the same policy decisions that are bad from our perspective, but do it again in a smarter way that makes them harder to challenge,” said Eva Bitrán, director of immigrants’ rights and staff attorney at American Civil Liberties Union of Southern California.

Another possible difference: The rules have changed. At the end of the U.S. Supreme Court’s 2023 term, the conservative majority issued a series of rulings that, taken together, make it much easier for people, businesses and aggrieved state governments to challenge federal regulations. At the time, these rulings were seen as a historic victory for the conservative legal movement and big business. Now that Trump is back in office, it may actually make the California attorney general’s job of stymying the Trump agenda easier.

Here’s a look at California’s record in court against Trump.

Wins on Administrative Procedure

California’s Department of Justice racked up a lot of legal wins early on in Trump’s term. The vast majority of them were over important but relatively narrow policy debates around asbestos oversight rules, big rigs that use old engine components, energy efficiency requirements on freezers and ceiling fans (that was two cases), among others.

As with many other areas of policy, California was able to eke out these easy victories by persuading courts that the Trump administration had rushed rules through without explaining their rationale, providing sufficient evidence, or giving the public the opportunity to weigh in. These are violations of the Administrative Procedure Act, which is the bureaucratic equivalent of failing to do your homework.

Though Trump 2.0 may be more careful this time, his pledge to fire thousands of career civil servants may also make the task of writing regulations that pass legal muster that much more difficult.

The Waiver Wars

One of California’s most successful legal challenges ended with a victory outside the court, said Julia Stein, an environmental law professor at UCLA. After the Trump administration revoked California’s permission to set its own emission limits on car exhaust — which comes from an Environmental Protection Agency waiver of the federal law’s preeminence over state rules — California sued. Then it sued again. Though the legal battle never quite reached a conclusion before Trump left office in 2021, the prolonged regulatory uncertainty was enough to convince some of the world’s biggest automakers to cut a deal directly with California.

Stein said she wouldn’t be surprised if that serves as a template for other regulated industries as California and the second Trump administration inevitably resume their legal battles.

“I think businesses are going to feel like, ‘well, I still need to make investment decisions and I still need to contend with different state regulatory environments and federal regulatory environments and so I might want to start entering into private agreements,’ ” said Stein.

Waters of the United States

California and other blue states spent the bulk of Trump’s first term beefing in court over how to define a “waterway.”

It was a semantic debate with enormous implications. Since the 1970s, the Clean Water Act has been the main way that federal regulators have battled water pollution. In 2015, the Obama administration expanded the definition of waterways covered under the law to include many wetlands and streams that only pop up during rainstorms.

Trump’s Environmental Protection Agency suspended that rule, reintroduced an old one, then came up with a new rule of its own, getting sued at every step. California didn’t end up formally winning in court, but the state did run out the clock in time for President Joe Biden to take over in 2021.

The story doesn’t end there. In 2023, the U.S. Supreme Court backed a narrower definition of the Clean Water Act, effectively taking Trump’s side of things. But California remains its own regulatory bastion; its stringent water quality rules remain in effect.

What’s Coming

There’s no shortage of ways that California might disagree with the incoming Trump administration on environmental matters, but the past is likely to be a pretty good guide. Expect the waiver wars to continue. California offered a taste of what’s to come before Biden was even out of office when it abandoned a proposed ban on diesel trucks, anticipating an unwinnable battle with Trump.

Other areas of possible disagreement abound. They include disputes over green infrastructure spending, offshore energy projects, wildfire relief funds, new national monuments created by Biden, and limits on the use of academic research to inform environmental policy.

Immigration: Travel bans and Sanctuary Cities

Thousands of people protested at airports in the first week of the previous Trump administration when he issued an executive order banning people from seven Muslim-majority nations from entering the United States. It kicked off years of battles over immigration enforcement, and California had a mixed record in court.

The Trump administration tried multiple times to enact his order restricting travel from those Muslim-majority nations. California and others sued, arguing that not only was the policy discriminatory, but that it was also bound to harm the economy, businesses, and universities.

Trump’s first two attempts were struck down, but in 2018 the Supreme Court upheld his third version of the ban. Biden reversed the order on his first day in office.

“Even in the cases where California lost, like this one, the fact that it took three rounds for the ban to be upheld, that’s helpful,” Bitrán at ACLU Southern California said.  “Throwing sand in the gears and slowing them down has a protective effect on California’s immigrant communities, too.”

Sanctuary Funding

During the first Trump administration, California passed a “sanctuary state” law to protect undocumented immigrants from deportation. That protection does have exceptions —  it does not apply to people convicted of violent crimes or serious offenses, for example.

When Trump said he planned to withhold certain federal dollars from “sanctuary jurisdictions” unless they cooperated with federal immigration authorities, the state, along with San Francisco, sued. That funding included about $28 million for the state of California that supports recidivism prevention, at-risk youth, and other law enforcement programs, former state Attorney General Xavier Becerra said at the time. A federal judge sided with California, calling Trump’s order unconstitutional.

Protecting DACA

In what some immigration attorneys call a landmark case, the state and the University of California Board of Regents participated in the defense of the Deferred Action for Childhood Arrivals program, or DACA, which allows immigrants brought to the U.S. as children to stay and work in the country.

While the program does not grant people legal status, it does protect them from deportation. In June 2020, the Supreme Court ruled in favor of the so-called DREAMers, blocking Trump’s plan to end the DACA program. This ruling shielded some 700,000 DREAMers, including about 200,000 residing in California.

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What’s Coming

Top of mind for immigration advocates is the promise of mass deportations, including Trump’s threat to use the military to carry out raids. A recent raid in Kern County, made waves throughout the state as a preview of what is potentially to come. Axios first reported that Trump plans to issue 100 executive orders on his first day back in the Oval Office, many of which are reported to be centered on immigration enforcement.

Trump could also reinstate a public charge policy from his first term that sought to make it harder for immigrants to get green cards if they use, or were likely to use, safety net programs, such as Medicaid or food stamps.

Legal experts also expect to see more fights around federal funding, restrictions for asylum seekers, and renewed efforts to end DACA or other temporary protected status.

Health Care: Obamacare and More

In round 1, Trump tried just about everything to pick away and dismantle the Affordable Care Act, also known as Obamacare. And while he was successful in nixing provisions of it, the health law today continues to stand. Some advocates and experts credit in part California’s move to interfere and defend the law during Trump’s last term for the fact that millions continue  to have health coverage.

Trump’s main attempt to repeal the Affordable Care Act failed when the Senate rejected a bill that would have undone former President Barack Obama’s signature law. A second challenge to the law followed when Texas filed a lawsuit contesting its constitutionality. Because the Trump administration did not move to defend the federal health law, 17 states led by California, intervened to make the case for keeping the Affordable Care Act.

While this was not a challenge initiated by California, advocates say California played a unique and instrumental role in the law’s defense. California essentially “stepped in for a Justice Department that was no longer doing its job on behalf of the nation” and defended the law in court, said Anthony Wright, executive director at Families USA, a consumer health advocacy organization.

In June 2021, the Supreme Court ruled in California’s favor to preserve the Affordable Care Act. Had the decision gone Texas’ way, approximately 20 million Americans, including 5 million Californians, could have lost their coverage.

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Health Care Subsidies

California also went to bat for health care subsidies that help make Obamacare coverage more affordable. In 2017, Trump announced the federal government would stop paying insurers for cost-sharing subsidies that help offset out-of-pocket expenses, like deductibles and copays. Becerra and 17 other state attorney generals filed a lawsuit on behalf of the estimated 6 million Americans who would have been affected by this change.

California placed its lawsuit on hold when marketplaces and insurers found a workaround to offset those losses by increasing premiums on certain plans (but also premium aid), and the case was eventually closed. While this was not a court win, per say, Wright said California’s administrative response was still a win for consumers.  “It was a way so that people’s copayments and deductibles didn’t spike to unaffordable levels,” Wright said.

About the Authors

Ana B. Ibarra covers health care for CalMatters. Her reporting largely focuses on issues around access to care and affordability. Ben Christopher covers housing policy for CalMatters. 

About CalMatters

CalMatters is a nonprofit, nonpartisan newsroom committed to explaining California policy and politics.