(California Today)

Xavier Becerra, California’s attorney general, has already sued the Trump administration more than 40 times, positioning himself on the front lines of the Golden State’s resistance to the president’s policies.

Monday, he added another big lawsuit to the tally.

Becerra, along with his counterparts in 15 other states, challenged President Donald Trump’s plan to declare a national emergency in order to access billions more dollars for a border wall than Congress had granted him.

“President Trump treats the rule of law with utter contempt,” Becerra said in a statement announcing that the suit had been filed in U.S. District Court in San Francisco. “He knows there is no border crisis, he knows his emergency declaration is unwarranted, and he admits that he will likely lose this case in court.”

It’s a fight that could have major constitutional ramifications. And California is playing a central role.

Here’s what else you need to know about the suit:

— It’s not clear whether any of the fencing Trump seeks to build would be in California. And it definitely won’t be built in some of the other states that have joined the lawsuit, like New York or Hawaii. So what specific harm gives California the right to sue over it?

Becerra told New York Times reporters that California and the other states have standing because residents of those states could “lose funding that they paid for with their tax dollars, money that was destined for drug interdiction or for the Department of Defense for military men and women and military installations,” if Trump gets his way.

In his statement, Becerra described Trump’s move as “unilaterally robbing taxpayer funds lawfully set aside by Congress.”

Still, it’s a really complicated situation. Experts say the success of the lawsuit will most likely come down to legal questions like which entities have the standing to sue in the first place, rather than questions about what’s actually happening on the border.

— Is this lawsuit the only challenge to Trump’s action?

Not even close. The Trump administration is facing a wave of lawsuits that have rolled in since the president announced his plans last week. And Congress is on a separate track to challenge the emergency declaration, which could include another lawsuit.

— Where is Gov. Gavin Newsom in all this?

He’s enthusiastically on board with the lawsuit. In a statement sent out by Becerra’s office Monday, Newsom echoed the language he used in his State of the State address last week.

“Rather than focusing on fighting the real vulnerabilities facing Americans, the president is using the powers of America’s highest office to fan the flames of nativism and xenophobia,” Newsom said in the statement. “Our message to the White House is clear: California will not be part of this political theater.”

This article originally appeared in The New York Times.