“There aren’t many full-time writing jobs in Bakersfield, so these kinds of remote editing contracts are important for me,” said Ms. Gallegos. “I just feel really frustrated and like I’m getting set back from my goals.”

Proponents of the new law argue that many companies are playing on worker anxieties and that many of the arrangements that employers are abandoning were illegal even before A.B. 5.

“A lot of these employers are sending out these fear-mongering emails,” said Assemblywoman Lorena Gonzalez of San Diego, the bill’s author. “I guess in this day and age of Twitter, that’s an easy thing to do — create a kind of mass hysteria.”

Ms. Gonzalez, a progressive Democrat, has in recent weeks become a fierce Twitter presence pushing back at critics, sometimes with profanity.

When asked about some of Ms. Gonzalez’s tweets, a spokeswoman said by email: “The assemblywoman is incredibly angry at an economic system that has caused a permanent underclass in her community of working men and women who are constantly being squeezed by corporate greed.”

Ms. Gonzalez has said the problems facing companies that rely on freelancers preceded the new law.

SB Nation, the sports website owned by Vox Media, which cited A.B. 5 as the reason it recently let go about 200 freelancers, was already sued by freelancers before the law changed. In one lawsuit, freelancers claimed that they worked as many as 40 hours a week but earned less than $150 a month.

A spokeswoman for Vox Media declined to comment but cited a post from SB Nation’s executive director in which he said the change was also “part of a business and staffing strategy that we have been exploring over the past two years.”