California Gov. Gavin Newsom called Thursday for a special legislative session to gird for a legal battle against the Trump administration over issues such as abortion, climate change, immigration and transgender rights.

The Democratic governor’s announcement, just two days after the presidential election, makes it clear that California is determined to renew its resistance to President-elect Donald Trump’s policies. The state filed more than 100 lawsuits against the first Trump administration.

“The freedoms we hold dear in California are under attack — and we won’t sit idle,” Mr. Newsom said in his announcement. “California has faced this challenge before, and we know how to respond. We are prepared, and we will do everything necessary to ensure Californians have the support and resources they need to thrive.”

The special session, slated to begin Dec. 2, will focus on providing more funding to the state attorney general’s office to pursue litigation against “any unlawful actions” by the administration and defend the state against any federal lawsuits.

Mr. Trump referred to the governor as “New-scum” during his campaign and often characterized California as the worst-case scenario of Democratic policies gone unchecked.

The state has positioned itself as a sanctuary for illegal immigrants and youths seeking gender transition drugs and surgeries, as well as a leader on climate change and abortion access.

Mr. Newsom’s office said his strategy was to make California laws “Trump-proof.”

“We’ve been through this before, and we stand ready to defend your rights and protect California values,” Attorney General Rob Bonta said. “We’re working closely with the governor and the Legislature to shore up our defenses and ensure we have the resources we need to take on each fight as it comes.”

Assembly Republican Leader James Gallagher called Mr. Newsom’s proclamation a “shameless political stunt.”

“The only ‘problem’ it will solve is Gavin Newsom’s insecurity that not enough people are paying attention to him,” Mr. Gallagher said in a statement. “There will not be a single policy implemented in this special session that couldn’t be addressed when the Legislature reconvenes in January.”

Casting himself as the president-elect’s foil allows Mr. Newsom to solidify his position as the Democratic Party’s heir apparent in 2028. Mr. Newsom is term-limited in 2026.

“If Newsom is so eager to set up a 2028 presidential run, he’d be much better served by fixing the crime, homelessness and high costs that will doom his campaign,” Mr. Gallagher said.

California isn’t the only Democratic-controlled state preparing to go on the offensive against Mr. Trump, who, on Jan. 20, will become the second president in U.S. history to serve two nonconsecutive terms.

In New York, Gov. Kathy Hochul and Attorney General Letitia James held a press conference Wednesday announcing that they would dedicate staff to “address potential federal legal threats” to laws on abortion access and gun safety.

Ms. James said the state filed nearly 100 legal actions against the first Trump administration, including to “preserve [Deferred Action for Childhood Arrivals] and to protect the Affordable Care Act.”

“We beat the Muslim ban. We stopped the dismantling of the United States Postal Service,” Ms. James said. “We challenged anti-LGBTQ+ efforts. We safeguarded key environmental policies. We protected access to reproductive care.”

She declared that New York “will continue to stand tall in the face of injustice, revenge or retribution,” although the Trump team has accused Ms. James of seeking political retribution with her civil fraud lawsuit.

Her office won a $454 million judgment in 2023 against the real estate mogul for inflating his net worth to secure more favorable loan terms, a decision he appealed.

Illinois Gov. J.B. Pritzker struck a more congenial tone by calling himself a “happy warrior” at a Thursday press conference but warned that “a happy warrior is still a warrior. You come for my people, you come through me.”

“Chaos, retribution and disarray radiated from the White House the last time Trump occupied it,” said Mr. Pritzker, a Democrat. “This time may be different. But if it isn’t, Illinois remains a place of stability and competent governance.”

• This article is based in part on wire service reports.