LOS ANGELES — California Gov. Gavin Newsom on Wednesday is expected to announce a lawsuit contesting President Donald Trump's executive authority to enact international tariffs without congressional approval.

The governor's office said the legal action will argue that the International Emergency Economic Powers Act, which Trump cited to impose tariffs, does not grant him the ability to unilaterally adopt tariffs on goods imported into the U.S.

"President Trump's unlawful tariffs are wreaking chaos on California families, businesses, and our economy — driving up prices and threatening jobs," Newsom said in a statement. "We're standing up for American families who can't afford to let the chaos continue."

The case marks the first time Newsom has taken a lead role in any of the now 15 lawsuits that California has filed against the current Trump administration, signaling a potential departure from his more reserved approach to the president during Trump's second term. Until now state Atty. Gen. Rob Bonta has acted as the face of California's legal battles against the federal government while Newsom has generally maintained a distance from the back-and-forth court tussles.

Under the International Emergency Economic Powers Act, Trump has implemented 10% baseline tariffs on all imported goods, higher taxes on goods from Mexico, Canada and China, and specific levies on products and materials such as autos and aluminum. The president threatened and then paused additional tariffs on other nations until this summer.

California, which the governor's office said engaged in nearly $675 billion in two-way trade last year, stands to lose billions in state revenue under Trump's tariff policies if international commerce declines and the stock market tanks. Mexico, Canada and China represent the state's three largest trade partners.

"The president's chaotic and haphazard implementation of tariffs is not only deeply troubling, it's illegal," Bonta said in a statement. "Californians are bracing for fallout from the impact of the President's choices — from farmers in the Central Valley, to small businesses in Sacramento, and worried families at the kitchen table — this game the President is playing has very real consequences for Californians across our state."

Newsom's office said the law specifies the actions the president can take if he declares a national emergency in response to a foreign national security, foreign policy or economic threat, "but tariffs aren't one of them."

No president before Trump has used the act to place tariffs on imported products from a specific country or on products imported to the United States in general, according to description of the law on a congressional website.

The complaint will allege that the act gives Congress the ability to impose tariffs and will ask the U.S. District Court for the Northern District of California to void Trump's tariff orders, according to Bonta's office.

If California ultimately prevails, requiring Congress to take a vote in Washington to enact Trump's tariffs could place Republican lawmakers in a vulnerable political position in the midterm elections. A recent poll from CBS News showed that 58% of Americans opposed the U.S. tariffs on imported goods.

Bonta is expected to join the governor at a news conference in the Central Valley on Wednesday morning to discuss the lawsuit.

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Times staff writer Kevin Rector contributed to this report.

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