Sessions said several California state laws prevent U.S. Immigration and Customs Enforcement officers from making deportation arrests and singled out elected officials for their actions.
"California, we have a problem. A series of actions and events has occurred here that directly and adversely impact the work of our federal officers," Sessions said.
Sessions had strong words for Oakland Mayor Libby Schaaf, who issued an unusual public warning last month that she was tipped off that an immigration operation was imminent, perhaps within 24 hours.
VIDEO: Jeff Sessions blasts Oakland mayor
"How dare you?" he said of Schaaf at a California Peace Officers Association meeting in Sacramento. "How dare you needlessly endanger the lives of law enforcement just to promote your radical open borders agenda?"
The Justice Department, in a federal lawsuit filed Tuesday, is challenging three California laws that, among other things, bar police from asking people about their citizenship status or participating in federal immigration enforcement activities.
"It wasn't something I chose to do, but I can't sit by idly while the lawful authority of federal officers are being blocked by legislative acts and politicians," Sessions said, straying from his prepared remarks.
#LIVE: "California absolutely appears to me is using every power it has, powers it doesn’t have, to frustrate federal law enforcement. So you can sure I'm going to use every power I have to stop that" - Sessions https://t.co/9lpm5fVzJc pic.twitter.com/4svsULd0VA— ABC7 Eyewitness News (@ABC7) March 7, 2018
Sessions received a polite if not warm reception from law enforcement officials, even when he told them his goal was to make their jobs safer. They applauded politely as he was introduced and after his speech, and more than a dozen gave a standing ovation at the end in a room of about 200 officials.
But many sat expressionless, some listening with arms crossed or chins on their folded hands, and his 25-minute speech was never interrupted by applause or protest.
About an hour later, Gov. Jerry Brown and California Attorney General Xavier Becerra fired back. They held a news conference, calling the federal lawsuit a political stunt and saying that Sessions' claims were not true.
"We're going to carry on. We want to protect our citizens from criminals. We want to protect people from improper abuse of the law. That's what it's about here," Brown said.
Brown called Sessions a liar, saying it was unprecedented for the attorney general to "act more like Fox News than a law enforcement officer." He accused Sessions of "going to war" with California to appease President Donald Trump.
"What Jeff Sessions said is simply not true and I call upon him to apologize to the people of California for bringing the mendacity of Washington to California," the governor told reporters.
The lawsuit is the latest salvo in an escalating feud between the Trump administration and California, which has resisted the president on issues from marijuana policy to climate change and defiantly refuses to help federal agents detain and deport immigrants. U.S. Immigration and Customs Enforcement has said it will increase its presence in California, and Sessions wants to cut off funding to jurisdictions that won't cooperate.
"AB 450 clearly allows employers to cooperate with ICE. It simply requires that before immigration enforcement agents enter certain areas of the workplace or access employee records, they first present employers with documents," Becerra said.
Brown and Becerra's news conference was held just blocks from where Sessions spoke, but they never interacted.
The Trump administration has threatened to withhold funding from jurisdictions that don't cooperate with federal law enforcement. Brown said the fight over this lawsuit will last longer than the Trump administration.
The governor did extend a hand to meet with Sessions but said the attorney general would have to "shape up and participate."
Schaaf later responded to Sessions' strong words for her.
"How dare you vilify members of our community by trying to frighten the American public into believing that all undocumented residents are dangerous criminals?" she told reporters.
Meantime, dozens of demonstrators gathered outside the hotel in Sacramento before Sessions' remarks. Some blocked traffic with many chanting "stand up, fight back" and "no justice no peace." There was a heavy police presence but no arrests.
"This is a reminder that California does not see his federal policies," said Steven Lynn, 33, a Sacramento graduate student. "We are a state of immigrants."
Brown speculated that Sessions' dig on California may be an attempt to ease an openly rocky relationship with the president, saying, "Maybe he's trying to keep his job because the president is not too happy with him."
Trump is set to visit California next week for the first time since his election to see models of his proposed wall along the Mexican border.
The Associated Press contributed to this report.