Earlier this week, Attorney General Jeff Sessions announced that the Justice Department would sue California, its governor, Jerry Brown, and the state attorney general because of California’s passage of three laws designed to offer a modicum of protection to undocumented immigrants. Chief among these is SB 54, the California Values Act, which limits, though does not eliminate, local law-enforcement cooperation with the federal Immigration and Customs Enforcement agency.

On Wednesday, Sessions journeyed to the state capital, Sacramento, to address a gathering of law-enforcement officers and hammer home his point. California, he argued—in limiting cooperation with ICE agents by penalizing employers who let ICE conduct raids on their work force without a warrant, and in mandating that the state’s attorney general conduct a review of all sites where immigrants are being detained by federal authorities—was essentially usurping federal responsibilities around immigration laws and behaving like a secessionist republic.

As he spoke at the Kimpton Sawyer Hotel, a new venue next door to the city’s also-new basketball arena, several blocks northwest of the capitol building, hundreds of protesters gathered outside in the early-morning chill. They had been mobilized at a few hours’ notice, through social media and word of mouth. The demonstrators carried signs with slogans such as “Todos Somos Hermanas,” “Full Rights for All,” and “First They Came For Immigrants.”

At 7:55 am, a few minutes before Sessions was scheduled to speak, the crowd moved from the sidewalk to the center of J Street, one of downtown Sacramento’s main arteries, temporarily blocking traffic and chanting, “Education, Not Deportation,” and “No Sessions, No KKK, No Fascist USA.” Then they marched east one block, south one block, and into the pedestrian area separating the arena from the hotel. And there, with construction workers atop the unfinished nearby buildings looking on and taking photos with their cell phones, local union leaders, school-board members, City Council members, State Assembly members, and state senators all took turns at the microphone defending California’s immigrant population and vowing to stand firm in the face of the federal threats.

“Are we ready to resist, to defend our state?” Assembly member David Chiu, himself the child of immigrants and the author of one of the bills that Sessions is suing California over, asked the crowd. “Mr. Trump, Mr. Sessions, we are America, we are California, and we will be here long after you are gone.”

Senate President Pro Tempore Kevin de León, whose primary challenge to US Senator Dianne Feinstein has recently begun picking up some traction, was also in the crowd. Increasingly, these days, he presents himself as a national rather than a regional politician. Wearing a dark-blue suit and a sober blue tie, his white shirt buttoned down, his purple patent-leather shoes carefully polished, de León talked to a throng of reporters as the event wound down. “We believe constitutionally we are on firm ground,” he said. “I don’t think we’re going to lose.”

Governor Brown wasn’t in the crowd, but, along with state Attorney General Xavier Becerra, he did hold a press conference at the state capitol shortly afterward, in which he accused the Trump administration of “going to war” against California and initiating a “reign of terror” against immigrants. Sacramento Mayor Darrell Steinberg also wasn’t in the crowd—he was on the way back from Washington, where he had spent much of the previous day criticizing the president and Attorney General Sessions for their anti-immigration stance, essentially daring the Feds to arrest him for his sanctuary-city policies.

There’s fury in California’s response to Trump and Sessions, but also a sense of possibility. In some ways, California’s leaders seem to be looking forward to the legal fight. They have, after all, been girding for this moment for the past 15 months.

California’s political and legal leaders believe the Constitution gives states the authority not to overturn federal immigration law or set their own immigration policy (which is essentially where Arizona, with its anti-immigrant SB 1070, went wrong and left itself vulnerable to federal legal action, according to legal scholars), but simply to limit the local resources they devote to helping federal agencies enforce that federal policy. They also believe that, in the long discovery process of any lawsuit, they will be able to force Washington to show its hand, to explain the criteria by which it is targeting specific immigrant groups, and to expose the racial-profiling techniques being used, and that they will also be able to show that ICE isn’t following even basic protocols for search warrants and detentions in California and other states.

Former US attorney general Eric Holder, who was retained by the state legislature after Trump’s election to represent California in its growing number of legal battles with the Trump administration, argues that SB 54 is vital to public safety in California, which has more immigrants than any other state in the country. In a conference call held with reporters after Sessions’s visit, Holder explained that if California’s immigrants are worried that any contact with local law enforcement could result in their deportation, they won’t alert the police to criminal activity in their neighborhoods.

Holder believes that, on the legal merits, California should be able to win this battle. “This is in some ways a pretty clear-cut case, in terms of the law. What you have here is a political expression by the Trump administration rather than a legal expression. They’ve caved in to the extreme part of a radical administration and are filing a lawsuit without much basis.”

Trump’s people are, clearly, trying to intimidate California—and, by extension, other sanctuary states and cities. They are threatening to withhold federal funds, to prosecute local political figures, and, now, they are suing the state. Yet, if the strategy is to bludgeon opponents into something like sullen acquiescence, it may well backfire.

“We have a rogue federal operation, making up the rules as they go,” says de León. “This is clear retribution for the bills we passed last year. California has been in the crosshairs of this president and attorney general since Day One. We welcome this lawsuit—and we will beat them in a court of law.”