Sen. Kamala Harris Kamala HarrisSocial Security and Medicare are on the ballot this November Harris honors Ginsburg, visits Supreme Court The Hill's Campaign Report: Trump and Biden vie for Minnesota | Early voting begins in four states | Blue state GOP governors back Susan Collins MORE (D-Calif.) slammed Attorney General Jeff Sessions Jefferson (Jeff) Beauregard SessionsGOP set to release controversial Biden report Trump's policies on refugees are as simple as ABCs Ocasio-Cortez, Velázquez call for convention to decide Puerto Rico status MORE on Wednesday after he compared California to the Confederate states in the Civil War.

"As far as I’m concerned, Jeff Sessions should be advised, and I’ll advise him right now, that it’s a bad idea, for him, to start talking about anything to do with the history of slavery or reconstruction or the Civil War in the United States," Harris told MSNBC's Chris Hayes.

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“His credibility is pretty much shot on those issues,” she continued.

Sessions on Wednesday announced a lawsuit against California over its immigration policies during a speech to the California Peace Officers’ Association in Sacramento.

The attorney general compared California to the Confederate states that seceded during the Civil War.

“I understand that we have a wide variety of political opinions out there on immigration. But the law is in the books and its purposes are clear and just,” Sessions said.

“There is no nullification. There is no secession. Federal law is the supreme law of the land. I would invite any doubters to go to Gettysburg, to the tombstones of John C. Calhoun and Abraham Lincoln. This matter has been settled,” he said.

The Department of Justice has filed a lawsuit against California in an effort to block three so-called sanctuary laws that the state's legislature passed last year in response to the Trump administration's immigration enforcement measures.

Sanctuary cities encourage local authorities not to implement federal immigration law.

Harris called the Justice Department's suit hypocritical.

“It’s hypocrisy at its height. Again, I think there’s a distraction in that they’re trying to suggest that this is about the constitution when in fact, what they’re doing is playing politics,” she said. “They’re playing politics and they’re playing politics with California.”

California's Gov. Jerry Brown (D) ripped the suit, calling it a political stunt in a tweet mocking President Trump Donald John TrumpBiden leads Trump by 36 points nationally among Latinos: poll Trump dismisses climate change role in fires, says Newsom needs to manage forest better Jimmy Kimmel hits Trump for rallies while hosting Emmy Awards MORE on Wednesday.