“This is a huge step forward to people all across the country dealing with this very challenging issue,” State Senator Bob Hertzberg, a Democrat and a co-author of the bill, said at a news conference after it was signed.
The ballot initiative, which would have made it easier for private individuals to sue companies for not adhering to its privacy requirements, had drawn vocal opposition from industry groups that worried about the potential liability risk.
The measure included a provision that would have required a 70 percent majority in both houses of the Legislature to approve any changes after it became law.
Google, Facebook, Verizon, Comcast and AT&T each contributed $200,000 to a committee opposing the proposed ballot measure, and lobbyists had estimated that businesses would spend $100 million to campaign against it before the November election.
Robert Callahan, a vice president of state government affairs for the Internet Association, an industry group that includes Google, Facebook and Amazon, said in a statement that the new law contained many “problematic provisions.” But the group did not try to obstruct it, he added, because “it prevents the even worse ballot initiative from becoming law in California.”
Mr. Callahan said the group would “work to correct the inevitable, negative policy and compliance ramifications this last-minute deal will create.”
Legislators said they expected to pass “cleanup bills” to make any fixes to the law in the 18 months before it takes effect. Some privacy advocates are worried that lobbyists for business and technology groups will use that time to water it down.
Mr. Mactaggart said those concerns are “overblown.”
“Having gotten this right, it’ll be very hard to take it away,” he said, noting that the ballot measure had been polling at around 80 percent approval. “They can’t rewrite the law.”