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Cars in California traffic. Photo: Robyn Beck/AFP/Getty Images

The Trump administration sued the state of California Wednesday to cease its emissions trading market, arguing it's unconstitutional for the Canadian province of Quebec to be its partner.

Why it matters, per Axios' Amy Harder: This lawsuit shows the federal government going on the offense, targeting a landmark state-level climate policy that’s been in place in the Golden State for many years.

  • If it succeeds, the lawsuit could limit states’ abilities to collaborate with foreign countries on policies whose impacts don’t follow borders — like climate change.

The big picture: The lawsuit is a huge escalation of the ongoing war between the Trump administration and California, with the former having mainly fought to defend federal actions until this latest move.

  • The lawsuit claims that the cap-and-trade program, meant to help limit air pollution, is unconstitutional because a state can't have an international pact without the federal government's approval.
  • The lawsuit reads: "Allowing individual states in the Union to conduct their own foreign policy to advance their own narrow interests is thus anathema to our system of government and, if tolerated, would unlawfully enhance state power at the expense of the U.S. and undermine the U.S.’ ability to negotiate competitive international agreements."

Go deeper: Trump moves to block California from setting own auto emissions rules

Go deeper

Updated 22 mins ago - Politics & Policy

Inauguration Day dashboard

U.S. Capitol and stage are lit at sunrise ahead of the inauguration of Joe Biden. Photo: Patrick Semansky - Pool/Getty Images

President Biden has delivered his inaugural address at the Capitol, calling for an end to the politics as total war but warning that "we have far to go" to heal the country.

What's next: Biden, Harris and nearly all the living former presidents and their spouses lay a wreath at Arlington National Cemetery.

Inaugural address: Biden vows to be "a president for all Americans"

Moments after taking the oath of office, President Biden sought to soothe a nation riven by political divisions and a global pandemic, while warning that "we have far to go" to heal the country and defeat a "virus that silently stalks the the country."

Why it matters: From the same steps that a pro-Trump mob launched an assault on Congress two weeks earlier, the new president paid deference to the endurance of American political institutions.

Updated 3 hours ago - Politics & Policy

In photos: The Biden and Harris inauguration

Joe Biden is sworn in as the 46th president of the United States. Photo: Alex Wong/Getty Images

Joe Biden and Kamala Harris were inaugurated as president and vice president respectively in a ceremony at the U.S. Capitol on Wednesday morning.

Why it matters: Top Democrats and Republicans gathered for the peaceful transfer of power only two weeks after an unprecedented siege on the building by Trump supporters to disrupt certification of Biden's victory. Trump did not attend Wednesday's ceremony.