Los Angeles, California - California Governor Gavin Newsom on Thursday called an emergency session of his state's legislature in response to Donald Trump's election, urging lawmakers to prepare to fight "unlawful" federal policies on issues including abortion, immigration, and climate change.

Liberal bulwark California led multiple legal battles against the White House during the first Trump presidency, on matters from auto emission limits to border wall construction, and Newsom called on the nation's most populous state to reprise that role ahead of the Republican's return to power.

"The freedoms we hold dear in California are under attack – and we won't sit idle," said Newsom in a statement.

"California has faced this challenge before, and we know how to respond. We are prepared to fight in the courts, and we will do everything necessary to ensure Californians have the support and resources they need to thrive."

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Specifically, the extraordinary session starting on December 2 will discuss boosting funding for legal action for California's justice department and other agencies to challenge the incoming Trump administration's policies in court.

Newsom said California lawyers have been preparing these measures "for more than a year" by readying arguments and evidence to challenge any "unconstitutional and unlawful federal policies" pursued by the Trump White House.

Newsom's special session will focus on protecting civil rights, reproductive freedom, climate action, and immigrant families, according to a statement.

It will be "the first of several actions" to shore up California's defenses against the incoming administration, a statement said.

"California is ready to fight," wrote Newsom on social media.

"Whether it be our fundamental civil rights, reproductive freedom, or climate action – we refuse to turn back the clock and allow our values and laws to be attacked," he said.

During Trump's first term, California launched dozens of lawsuits against the federal administration, often joining forces with other states, in particular fellow liberal West Coast states Oregon and Washington.

Washington Governor-elect Bob Ferguson was expected to announce similar pre-emptive measures at a press conference later Thursday.

The calls to action follow an election in which Republicans took not just the White House, but won the popular vote, secured control of the Senate, and appeared likely to hold onto a majority in the House of Representatives.

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Trump campaigned on pledges including mass deportation of illegal immigrants, and a shift from renewable energy toward the US oil sector.

Abortion rights advocates fear a Republican-controlled Congress enacting sweeping national restrictions or an outright ban, while Trump has publicly vowed to take revenge on his political enemies.